Muscle overactivity and movement dysfunction in the upper motoneuron syndrome

Transcription

1 Phys Med Rehabil Clin N Am 14 (2003) Muscle overactivity and movement dysfunction in the upper motoneuron syndrome Nathaniel H. Mayer, MD a,b, *, Alberto Esquenazi, MD c,d,e a Department of Physical Medicine and Rehabilitation, Temple University Health Sciences Center, Broad and Ontario Streets, Philadelphia, PA b Drucker Brain Injury Center and Motor Control Analysis Laboratory, MossRehab, 1200 West Tabor Road, Philadelphia, PA c Gait and Motion Analysis Laboratory and Regional Amputee Center, MossRehab, 1200 West Tabor Road, Philadelphia, PA d Department of Physical Medicine and Rehabilitation, Albert Einstein Healthcare Network, Einstein Plaza Olney, Suite 503, Philadelphia, PA e Department of Physical Medicine and Rehabilitation, Jefferson Medical College, 1020 Walnut Street, Philadelphia, PA The upper motoneuron syndrome (UMN) is a collective term that refers to different types of motor behaviors produced by patients who have lesions of the descending corticospinal system. Lesions involving the upper motoneuron, its pathways and connections can occur at the level of the cortex, internal capsule, brain stem, or spinal cord. It has been traditional since the days of Hughlings Jackson to categorize the clinical features of UMN as positive phenomena, referring to overt behaviors generated by various forms of muscle overactivity, and negative phenomena, referring to loss of overt behaviors secondary to impaired muscle activation, impaired control of motor behavior, and impaired motor performance [1]. Positive features include stretch-sensitive phenomena such as spasticity, hyperreflexia, co-contraction, and spastic dystonia [2]. Positive features might also include nonstretch-sensitive behaviors such as enhanced nociceptive reflexes (flexor reflexes) and synkinesias (unintended extrasegmental activation of muscles that occurs when a patient intends only to move one limb segment but is obliged by the UMN lesion to move limb segments elsewhere). Negative features include loss of strength; slow, effortful movement; loss * Corresponding author. Drucker Brain Injury Center and Motor Control Analysis Laboratory, MossRehab, 1200 West Tabor Road, Philadelphia, PA address: nmayer@einstein.edu (N.H. Mayer) /03/$ see front matter Ó 2003 Elsevier Inc. All rights reserved. doi: /s (03)

2 856 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) of dexterity (particularly finger dexterity); impaired motor control; and easy fatigability [3]. The clinical impact of UMN on patients is broad and tends to limit functional capacity. The negative and positive signs lead to reduced mobility and limb usage. Sequelae often include decubiti, cardiovascular problems, thrombophlebitis, respiratory infections, contractures, osteoporosis, neurogenic bladder and bowel, physical dependence, and social isolation. Negative features of upper motoneuron syndrome Muscle weakness or difficulty generating the necessary force for effective motor performance is a cardinal feature of UMN. Weakness is reflected in deficient generation of muscle tension and sustained force. Weakness can occur because of a loss of motor unit activation, changes in the order of motor unit recruitment, and changes in motor unit firing rates [4 7]. Changes can also occur in the properties of motor units such as prolonged contraction times and changes in motor unit type. For example, a type of slow-contracting and fatigable motor unit has been reported after stroke a motor unit type not normally present in muscle [8]. At the level of whole muscles, impairment in muscle force generation and the timing of that force relative to the task at hand might occur [9]. In addition, differential weakness might occur within muscle groups. For example, Fig. 1 depicts a 24-year-old man 15 months post traumatic brain injury with a marked flexed wrist deformity secondary to UMN. Fig. 2 shows electromyographic features during his effort to reach and grasp a cylindrical target rod. The figure shows that extensor carpi ulnaris activates well during the reaching phase, even as extensor carpi radialis activates poorly during the same movement effort to extend the wrist. Wrist extension motion is limited not only by weak recruitment of the extensor carpi radialis (ECR), an important wrist extensor, but also by increased stiffness of wrist flexors that this patient manifested. Finally, loss of selective control of individual movements (ie, the ability to activate and control individual limb segments by controlling Fig year-old man who has marked flexed wrist deformity secondary to UMN of 15 months duration after traumatic brain injury.

3 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Fig. 2. Electromyographic features of patient in Fig. 1 making an effort to reach for and grasp a target (a cylindrical rod with a 0.5 in diameter). two-way movement) is one of the last motor control capabilities to recover after a UMN lesion. UMN patterns such as the flexed wrist (see Fig. 1) are discussed in detail later in this article. Such abnormal UMN patterns of movement might represent an adaptation to motor performance that becomes apparent when a person attempts to move in the presence of weakness/paralysis of some muscles combined with imbalanced activation between weaker and stronger muscle groups [10]. Add to this constraints on movement imposed by increased stiffness and contracture [11,12] so typical of patients with chronic UMN and one has the ingredients for the development of so many of the abnormal UMN patterns of movement dysfunction seen in the authors clinic. Loss of dexterity is a negative sign seen in UMN. Loss of dexterity after UMN frequently refers to use of the hand. Kuypers sectioned the pyramidal tract of monkeys at the level of the medullary pyramids and found that the animals lost dexterity of distal musculature [13]. They particularly lost the ability to fractionate finger movements (ie, to move the fingers independently for fine manipulation of objects). Of additional interest is that these animals did not become spastic clinically. Other researchers refer to loss of dexterity as a loss of skill and adroitness in using the body [14]. Muscle weakness might underlie loss of dexterity under some circumstances, but the relationship between strength (the ability to generate adequate muscle force with respect to load) and dexterity (coordinated temporal and spatial activation of many muscles) remains to be elucidated.

4 858 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Positive features of upper motoneuron syndrome Stretch-sensitive and nonstretch-sensitive positive features have been described in UMN. In classical studies of the decerebrate cat, Lidell and Sherrington were the first to describe a stretch-sensitive reflex that had two components: (1) an intense but short-lived phasic component determined by a dynamic (rapid, time varying) change in muscle length, and (2) a less intense but longer-lasting tonic component determined by static (sustained or time invariant) stretching of muscle at the new longer length [1]. Sherrington s identification of the stretch reflex as an afferent efferent neural circuit in the cat that had UMN served as a model for later clinical descriptions of spasticity. Nathan emphasized the central role of the stretch reflex in spasticity as follows: Spasticity is a condition in which stretch reflexes that are normally latent become obvious. The tendon reflexes have a lowered threshold to tap, the response of the tapped muscle is increased, and usually muscles besides the tapped one respond; tonic stretch reflexes are affected in the same way [15]. In UMN, tendon taps provide a brief but intense stretch of muscle, the afferent input of which to the spinal cord results in a brief (phasic or time varying) efferent output of electromyographic (EMG) activity in the tapped muscle followed by a brisk (phasic) jerk movement of the relevant limb segment. When afferent input is generated by an examiner during sustained manual stretching of the same UMN muscle, efferent-induced resistance of a sustained or tonic nature is experienced by the examiner throughout the period of muscle stretch. Reflex-induced EMG activity will persist in a sustained or tonic manner Fig. 3. Patient who has hemiparesis of 4 years duration. Rapid stretches of brachioradialis by an examiner passively extending the elbow. A spastic catch can be seen, especially in the motion trace on the right side of the figure. Note rapid cessation of EMG activity when stretch is released.

5 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) throughout the period of stretch and will not cease until stretch is undone (Fig. 3). Fig. 4 compares negative and positive signs in the same muscles of a patient who had UMN. Tracings were obtained with surface electrodes and an electrogoniometer from a 42-year-old patient who had UMN syndrome resulting from a gunshot wound to the brain 11 months previously. Voluntary elbow flexion on the left side of the figure is compared with passive stretch of the elbow flexors on the right side of the figure. Voluntary flexion movement is upward, and passive extension of the elbow is downward. The figure reveals that voluntary flexion was slow, taking the patient almost 3 seconds to reach a maximum flexion of 90. Good EMG recruitment develops in the biceps, but weak recruitment, a negative sign of UMN syndrome, occurs in the brachioradialis. On the right side of Fig. 4 a stretch reflex response is elicited by rapid passive stretch of the elbow flexors in the usual clinical manner. Brisk stretch reflex responses, a positive sign of UMN syndrome, are observed in biceps and, especially, in the brachioradialis. Compare spastic EMG recruitment on the right with the EMG recruitment of voluntary effort on the left, particularly for the brachioradialis. Spastic muscles are often weak. Co-contraction is another form of muscle overactivity seen in UMN [16 19]. Co-contraction can be described as activation of antagonist muscles during a voluntary command on agonists. Co-contraction can occur during isometric effort, so it is not necessarily related to muscle stretch. In Fig. 5 a patient who has UMN is performing voluntary flexion and extension movements of the elbow in an alternating manner. Solid black arrows point to EMG activity in the biceps and brachioradialis muscles during extension phases of the movements. These muscles are elbow flexors, but they show Fig. 4. Comparison of negative and positive signs in a patient who has UMN. Voluntary flexion effort (left) and passive stretch (right) can be seen. Note that both biceps and brachioradialis react to passive stretch (ie, they are spastic), but only the biceps recruits well during voluntary effort to flex the elbow. Brachioradialis is weak and spastic.

6 860 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Fig. 5. The presence of electromyographic in antagonist muscles recorded during voluntary agonist effort. Extension phase (dotted arrows). Co-contraction activity in biceps and brachioradialis during extension phase of voluntary alternating elbow movements (solid arrows). activity during elbow extension. Such activity can restrain extension motion, and a careful examination of the movement trace suggests that the duration of extension phase is longer than the more rapidly occurring flexion phase. Furthermore, the biceps is seen to be active during the flexion and extension phases. In fact, there is more biceps EMG during flexion than extension phases, when the biceps serves as an agonist (as is expected). Brachioradialis, on the other hand, is inactive during the flexion phase and is only active during the antagonist extension phase. In a simplistic way, brachioradialis is inactive when it should be active and active when it should be inactive. Co-contraction might represent misdirected supraspinal drive, but (as might be possible in the case above) stretch-related phenomena might also play a role because muscles are stretched during extension phase. A key to recognition of co-contraction is that it occurs during voluntary effort [20]. In a series of studies that examined movement after ablations of different areas of the central nervous system, Denny-Brown described specific disturbances of postural reactions in monkeys [21]. The animals adopted fixed attitudes or postures that varied with head and body positioning. For example, after certain cortical ablations a prone monkey lay with forelimbs tightly flexed against the body and hind limbs extended stiffly and abducted. If the animal was held head down, the arms extended and the lower limbs flexed, adducted, and folded tightly against the body. Other postural attitudes were elicited when animals were sat up, their heads held upwards, tilted backward or forward, and so on. In all these postures, any attempt by the examiner to pull a limb away from its fixed position was met by an increasing resistance of springy quality so that the limb would fly back to its original posture when released. Denny-Brown called this fixed attitude

7 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) dystonia. He also found that electromyographic activity was present and continuous in muscle groups of these animals that were described clinically as dystonic. Dystonia, therefore, connoted a persistent posture maintained by muscular contraction and, by inference, it was not a feature of voluntary movement effort nor was it truly spastic in nature because spastic muscles are electromyographically silent at rest. Denny-Brown did not necessarily find in his animals such spastic features as hyperreflexia or the clasp-knife phenomenon described by Liddell and Sherrington in their decerebrate cat preparation; however, in some of his experiments Denny-Brown did find signs of spasticity that coexisted with the postural phenomenon of dystonia. He therefore recognized this combination of signs as an entity by referring to it as spastic dystonia. Fig. 6 illustrates a UMN patient who had clinical signs of spasticity who was asked to stand quietly at rest. A flexed elbow posture is evident clinically. EMG recordings of the biceps and brachioradialis during the atrest posture reveal low-grade, persistent activation of biceps and occasional potentials in brachioradialis. Denny-Brown might well have called this form of overactivity spastic dystonia. It should be noted, however, that patients who have limb posturing do not necessarily have underlying persistent EMG activity in relevant muscles; passive tissue stiffness alone might be sufficient to maintain a posture. Contracture can certainly hold a limb in a fixed position; however, in the absence of obvious phasic stretch or voluntary effort, spastic dystonia might be an apt term to describe a patient who has demonstrated tonic muscle activity underlying persistent clinical posturing. Fig. 6. Example of spastic dystonia.

8 862 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) In summary, damage to the upper motoneuron, its pathways, and its connections lead to the upper motoneuron syndrome, the features of which include stretch-sensitive and nonstretch-sensitive abnormal motor behaviors (positive features) along with impairments in muscle activation, motor control, and skilled performance (negative features). Negative features reflect a paucity of signal, whereas positive features reflect an enhanced central excitatory state secondary to plastic rearrangements of neuronal circuitry in the spinal cord and alterations in background activity produced by descending excitatory and inhibitory inputs to the cord. Clinical weakness and loss of dexterity result from unbalanced activation of muscle groups whose strength has been differentially affected by the UMN lesion. Positive features such as co-contraction and spastic dystonia also exacerbate clinical weakness and loss of dexterity by contributing to an altered balance of muscle and other soft tissue forces acting across joints during posture and movement. In the clinic, altered balance of forces in patients who have UMN leads to common clinical presentations or common patterns of UMN dysfunction [22]. In the upper extremity, for example, the flexed elbow, the clenched fist, and the thumb-in-palm deformity are observed frequently. In the lower extremity, adducted thighs, stiff knee, and equinovarus with toe curling are seen commonly. The remainder of this article discusses commonly seen patterns of UMN dysfunction with emphasis on underlying muscles that might contribute dynamically to such patterns. Identification of muscles that contribute dynamically to a UMN deformity can serve as a basis for peripheral strategies of intervention such as chemodenervation, neurolysis, and neuro-orthopedic surgery [12,23,24]. Adducted/internally rotated shoulder The patient who has an adducted/internally rotated shoulder typically presents with the humerus held tightly against the chest wall. The elbow is often flexed and, because of internal rotation of the shoulder, the hand and forearm are draped on top of the chest anteriorly. Prolonged adduction is frequently associated with adductor muscle contracture. With respect to symptoms, patients complain of shoulder stiffness and painful passive range of motion because the large adductor muscles of the shoulder can generate strong spastic tension when stretched. Vigorous passive range of motion exercises of the shoulder performed by therapists or family members in the interest of preventing contractures might be a source of considerable pain secondary to impingement syndrome which, in and of itself, can drive spasticity (Fig. 7). With respect to passive function, severe adduction posturing can lead to skin maceration, breakdown, and malodor in the axilla. Donning a shirt, blouse, or jacket can challenge caregivers and perturb patients. Access to the axilla for washing and deodorant application is commonly problematic.

9 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Fig. 7. The adducted/internally rotated shoulder is associated with painful stiffness and contracture, interferes with hygiene and dressing, leads to axillary skin maceration, and predisposes to humeral fracture. With respect to active function, voluntary abduction and, in particular, voluntary forward flexion of the humerus might be compromised by cocontraction of adductors and extensors. Reaching-forward behavior is a cardinal function of the upper limb, and restricted flexion of the humerus plays a great role in limiting reaching. Physical examination of such patients typically reveals an adducted, internally rotated, sometimes partially extended humerus as the rest position of the shoulder. Many patients have little or no active shoulder abduction, but some do. When the range of motion of passive abduction considerably exceeds active abduction and when time to complete abduction is noticeably slower than time to complete adduction, the possibility of adductor muscle co-contraction during active abduction must be considered. An alternative possibility that might account for these findings is abductor muscle weakness. Similarly, when the range of motion of passive flexion considerably exceeds active flexion and when time to complete flexion is noticeably slower than time to complete extension, the possibility of extensor muscle co-contraction during active flexion or forward reach must be considered. An alternative possibility that might account for these findings is flexor muscle weakness. Muscles that potentially contribute to the adducted/internally rotated shoulder pattern include pectoralis major, teres major, latissimus dorsi, anterior deltoid, and subscapularis. Palpation of the tendon of pectoralis major in the anterior axillary line and the tendons of latissimus dorsi and teres major in the posterior axillary line provide some clinical information, but potential contributions from anterior deltoid and subscapularis are difficult to ascertain clinically (Fig. 8). Dynamic EMG studies might help

10 864 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) differentiate between muscle overactivity in teres major, latissimus dorsi, pectoralis major, and anterior deltoid (subscapularis has been difficult for the authors to record from) and muscle underactivity or weakness in middle deltoid and supraspinatus. Diagnostic lidocaine blocks can be performed on the thoracodorsal nerve, a purely motor nerve innervating latissimus dorsi, and on the motor points of teres major, pectoralis major, and anterior deltoid if necessary [25]. The authors find block of subscapularis to be challenging and prefer to rule its contribution in or out after blocking other muscle groups that are more manageable. Overactivity in muscles relevant to restricted humeral abduction are amenable to chemodenervation, neurolysis, and, for long-term purposes, orthopedic interventions, primarily lengthening. The motor points of teres major and pectoralis major and the purely motor thoracodorsal nerve to latissimus dorsi are accessible to neurolysis. The authors have injected anterior deltoid only rarely. The Fig. 8. This 20-year-old man who has traumatic brain injury (TBI) and right hemiparesis of 29 months duration complains that it is an effort to reach forward at the shoulder. Co-contraction in latissimus dorsi and, to a lesser extent, in long head of triceps and teres major can be seen.

11 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Table 1 Muscles that might exhibit overactivity in the adducted/internally rotated shoulder Muscles Typical overactivity Pectoralis major ++ Teres major +++ Latissimus ++ Subscapularis? authors prefer neurolysis with phenol when botulinum toxin (which has a ceiling dose) requires conservation for muscles elsewhere. Muscles that potentially contribute to restriction of humeral flexion include teres major, latissimus dorsi, long head of the triceps, and posterior deltoid. Dynamic EMG studies might help differentiate between muscle overactivity in teres major, latissimus dorsi, long head of triceps, or posterior deltoid and muscle underactivity or weakness in anterior deltoid, pectoralis major, or biceps. Diagnostic blocks with lidocaine can also be used. The posterior deltoid is less often involved in restricting shoulder flexion; it functions more in a support role by abducting the shoulder. Overactivity in muscles relevant to restricted humeral flexion are amenable to chemodenervation, neurolysis, and orthopedic interventions (Table 1). The authors use phenol neurolysis for large proximal muscles when botulinum toxin needs to be conserved for smaller distal muscles. A similar approach is taken for muscles involved in the hyperextended shoulder (Table 2). Flexed elbow The patient who has a flexed elbow typically presents with persistent elbow flexion during sitting, standing, and especially walking. The forearm is more often pronated than supinated despite the biceps being a supinator of the forearm. The pronator teres is in a biomechanical position to flex the elbow by a reverse origin/insertion mechanism, and pronators of the forearm are commonly spastic and stiff. Prolonged elbow flexion posturing is frequently associated with contracture. With respect to symptoms, many patients complain that their elbows persistently ride up when they stand up to transfer or walk. A disfiguring appearance of the flexed elbow is a complaint of many patients (Fig. 9). Patients also complain that their flexed elbow gets Table 2 Muscles that might exhibit overactivity in the hyperextended shoulder Muscles Typical overactivity Teres major +++ Latissimus dorsi ++ Long head of triceps ++ Posterior deltoid +

12 866 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Fig. 9. (A) The flexed elbow can result in disfigurement, contracture, elbow crease skin maceration, and involuntary neck and face compression, (B) riding up during standing and walking that leads to hooking people, furniture, and doorways, and (C) limitation of active reaching.

13 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) hooked on doorframes, furniture, or even people shopping in a crowded mall. Stiffness is a common sensation and complaint. Shaking secondary to clonus is also noted by patients as an annoyance, but it can sometimes lead to frank loss of balance and stumbling if clonus spreads violently to other limbs. Infrequently, patients jam their fist into their throats because of severe flexion at the elbow combined with adduction of the humerus. With respect to passive function, severe flexion posturing can lead to skin maceration, breakdown, and malodor in the antecubital fossa. Pulling a shirt or jacket past the bend of a bent elbow causes struggle for caregivers and discomfort for patients. Passive ranging of stiff muscles is often painful. With respect to active function, voluntary or active elbow extension is a key part of reaching and bringing the hand to a target. Patients who have cocontraction of one or more elbow flexors during active elbow extension complain of effortful reaching and shortened elbow extension range. If the patient is asked to alternately flex and extend the elbow, the extension phase is typically slower and more effortful for the patient than the flexion phase. An effort to extend the elbow to its maximally available passive range is more difficult and more asymmetric in timing than active extension only for partial range (ie, active extension for less than half the available passive range). Weakness of triceps muscles (as agonists) also makes reaching for objects problematic, and weakness of elbow flexors (as agonists) leads to an impaired ability to bring objects to the body or to place them elsewhere. Patients who use a walker might have difficulty reaching to grasp the walker and advancing it. Even if a hand cannot grasp, an elbow and a shoulder that can reach forward to push are functionally usable by the patient to close a door or a drawer or to stabilize objects when the other more functional upper limb is otherwise occupied. Physical examination typically reveals a flexed resting position of the elbow. Many patients have little or no active elbow extension, but some do. When the range of motion of passive extension considerably exceeds active extension or when the time to complete extension is noticeably slower than the time to complete flexion, the possibility of flexor muscle co-contraction during active extension must be considered. An alternative possibility that might account for these findings is extensor muscle weakness. A flexed elbow deformity can cause stretch injury to the ulnar nerve as it winds around the acute bend of the elbow. When the elbow is bent, the nerve is also vulnerable to repeated trauma against lapboards, bed rails, and wheelchair arm rests. Signs of intrinsic muscle atrophy in the hand and weakness of ulnar wrist and finger flexion might be present secondary to cubital tunnel compression of the ulnar nerve. Muscles that potentially contribute to the flexed elbow deformity include biceps, brachialis, and brachioradialis (see Table 3, Fig. 10). Secondary muscles might include extensor carpi radialis and pronator teres. Dynamic EMG of elbow flexors and extensors (triceps and anconeus) might help distinguish combinations of muscle overactivity in flexors and muscle

14 868 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Table 3 Muscles that might exhibit overactivity in the flexed elbow Muscles Typical overactivity Brachioradialis +++ Biceps ++ Brachialis + underactivity or weakness in extensors. For example, dynamic EMG studies have indicated that, for many patients, muscle overactivity is greater for brachioradialis than for biceps and brachialis [26]. All three muscles are amenable to chemodenervation, neurolysis, and orthopedic lengthening. In practice, interventions have been delivered more often to biceps and brachioradialis muscles. Pronated forearm The patient who has a pronated forearm typically presents with a forearm that is pronated fully. In many cases this finding is associated with a flexed Fig. 10. Active flexion followed by active elbow extension in a patient who has UMN. Note cocontraction activity throughout extension phase in brachioradialis and brachialis and some cocontraction activity in biceps during early extension. The displacement trace has a catch during extension, reflecting restraint of movement by antagonistic co-contraction of flexors.

15 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) elbow. Pronation posturing appears to be more common than supination posturing. Persistent pronation makes it difficult for a person to reach underhand to a target, whereas supination posturing impairs reaching for targets that require overhand reach. With respect to symptoms, patients might complain that passive stretching of stiff pronators is uncomfortable or painful. With respect to passive function, caregivers find it difficult to turn the patient s hand palm side up for fingernail trimming. Palm-up orientation of the hand is necessary for nail trimming when a UMN patient also has fingers that are flexed into the palm secondary to a clenched fist deformity. The clenched fist deformity is exceedingly common. With respect to active function, many instrumental activities of daily living depend on active pronation/supination motions. The use of feeding utensils such as a spoon or a hand towel for face washing require supination movements, as do reaching for a glass, shaking hands, using clothes fasteners, and many other instrumental activities of daily living. These everyday tasks become problematic when supination is restricted by overactive pronator muscles or by their contracture. Physical examination typically reveals a pronated resting position of the forearm. Many patients have little or no active forearm supination, but some do. When the range of motion of passive supination exceeds active supination or active supination is noticeably slower than active pronation, the possibility of pronator muscle co-contraction during active supination should be considered. An alternative possibility that might account for these findings is supinator muscle weakness. Muscles that potentially contribute to the pronated forearm pattern include the pronator teres and the pronator quadratus. Both pronators can show varying degrees of volition, cocontraction, and spasticity. Dynamic EMG studies might help differentiate between muscle overactivity in the pronator quadratus and the pronator teres and muscle underactivity or weakness in the biceps (as a supinator). Diagnostic lidocaine blocks can be performed on the pronator quadratus using a dorsal approach with insertion of a needle through the interosseous membrane (Fig. 11). Electric stimulation is used to find the motor nerve branch to the pronator quadratus. Motor point block of the pronator teres can be achieved on the ventral surface proximally using electric stimulation as a guide. Serial casting to diminish pronator contracture is difficult to orchestrate, but both pronator muscles are amenable to chemodenervation, neurolysis, and orthopedic lengthening (Table 4). Flexed wrist The patient who has a flexed wrist typically presents with a wrist that is flexed, sometimes with radial deviation, sometimes with ulnar deviation. In many cases a flexed wrist is associated with a clenched fist deformity. The extrinsic finger flexors cross the wrist anterior to its axis of rotation,

16 870 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Fig. 11. Reaching for a rod underhand. Note co-contraction of both pronators and effect on movement trace. therefore acting as accessory wrist flexors themselves. Wrist deformities are largely flexor, but some patients develop a hyperextension deformity that exacerbates a clenched fist posture because of the effect of finger flexor tenodesis. With respect to symptoms, patients might complain that passive stretching of stiff flexors is uncomfortable or painful. Compression of the median nerve at the wrist can produce carpal tunnel syndrome with hand pain. The disfiguring appearance of a flexed wrist (and its common companion the clenched fist) is a frequent complaint. With respect to passive function, severe flexion posturing hinders passive exercises, dressing a sleeve, and perhaps washing by caregivers. With respect to active function, a flexed wrist makes for awkward hand placement during reaching, impairs positioning of objects held by the hand before their manipulation or release, and weakens grip strength. Physical examination typically reveals a flexed wrist resting posture. Many patients have little or no active wrist extension, but some do. When Table 4 Muscles that might exhibit overactivity in the pronated forearm Muscles Typical overactivity Pronator teres ++ Pronator quadratus ++

17 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) passive extension of the wrist exceeds active wrist extension or active extension is noticeably slower than active flexion, the possibility of flexor muscle co-contraction during active extension should be considered. An alternative possibility that might account for these findings is wrist extensor weakness. If the patient also has a pronounced flexed elbow deformity, weakness of flexor carpi ulnaris might be caused by ulnar nerve compression in the cubital tunnel. Intrinsic muscle atrophy in the hand supports this suspicion. Radial deviation with flexion is usually attributable to overactivity of flexor carpi radialis (FCR). Ulnar deviation, however, might be caused by flexor carpi ulnaris (FCU) or by this muscle in combination with extensor carpi ulnaris (ECU). Prominence of the tendon of ECU, especially during reaching, alerts the clinician to this possibility. The tendon of palmaris longus (PL) is located just medial to the tendon of FCR at the wrist. Prominence of the tendon of PL alerts the clinician that this muscle might be playing a role in wrist flexion deformity. On occasion the authors have seen a prominently bowstringing tendon of PL in the absence of a similar finding for FCR. Muscles that potentially contribute to the flexed wrist deformity include FCR, PL, FCU, and ECU. All of these muscles are amenable to chemodenervation, neurolysis, and orthopedic lengthening. With respect to conservative options, the authors prefer chemodenervation under EMG or electric stimulation guidance because the technique of injection is more efficient. Severe wrist flexion with tight tendons that pressure the median nerve against the leading edge of the transverse carpal ligament usually requires surgical decompression. The roles of FCU and ECU in ulnar deviation along with involvement of PL can be further elucidated by multichannel dynamic EMG (Fig. 12; Table 5). Clenched fist The patient who has a clenched fist typically presents with fingers that are flexed into the palm. The patient is unable to perform (or has limited hand opening during) the reach phase of reaching to grasp an object. In many cases this finding is also associated with a thumb-in-palm deformity. With respect to symptoms, patients complain of fingernails digging into palmar skin, causing pain. Nail bed infections might occur. Patients also complain of pain when they or their caregivers attempt to pry fingers open to gain palmar access. Disfigurement is a frequent complaint. With respect to passive function, caregivers find that the clenched fist deformity makes for difficult access to the palm for washing and drying. When access is chronically restricted, skin maceration, breakdown, and malodor can develop (Fig. 13). Donning gloves and putting on and wearing hand splints can be problematic. With respect to active function, grasp, manipulation, and release of objects from the hand depend on finger and thumb control.

18 872 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Fig year-old man who is 22 months post TBI reaching forward to grasp a rod. Clinically, he demonstrates ulnar deviation. Electromyographically, FCU is overactive during reach phase, but the clinician must also consider treating ECU as a potential contributor to ulnar deviation if block of FCU is insufficient to correct excessive ulnar deviation. The loss of the hand even as a gross assist makes activities of daily living problematic for patients. Chronically flexed fingers are likely to develop muscle, skin, and joint contractures. The hand as a holder is obviated by this clinical occurrence. Physical examination typically reveals a flexed resting position of the fingers in the form of a clenched fist. When the distal interphalangeal (DIP) joints are extended (ie, when the fingernails can be seen) while the proximal interphalangeal (PIP) joints are flexed, muscle overactivity in the flexor digitorum sublimis (FDS) is suspected. When the fingernails are buried in Table 5 Muscles that might exhibit overactivity in the flexed wrist Muscles Typical overactivity Flexor carpi radialis +++ Palmaris longus ++ Flexor carpi ulnaris ++ Extensor carpi ulnaris +

19 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Fig. 13. This patient who had UMN had fingers clenched into the palm that were painful to open. When the fist was partially opened, maceration and skin breakdown were evident. Note thumb-in-palm deformity secondary to overactive flexor pollicis longus. the palm, flexor digitorum profundus (FDP) alone or in combination with FDS are likely involved. Because of tenodesis action, extrinsic finger flexors are noticeably tighter when the wrist is extended than when the wrist is flexed. To get a good look at the palm, the examiner flexes the wrist then attempts to pry the fingers open. Joint contractures prevent motion regardless of the wrist position. Resistance to passive stretch of FDS can be estimated by holding the wrist in neutral position or relatively extended, holding the metacharpophalangeal (MCP) joint in neutral position or relatively extended and stretching the PIP joint at different rates. Resistance to passive stretch of FDP is performed similarly, but the examiner also attempts to hold the PIP joint in a neutral or relatively extended position while stretching the DIP joint. Because the finger flexors cross the wrist joint anterior to its axis of rotation, the examiner will notice that wrist position plays a key role in determining the degree of resistance to passive stretch of the extrinsic finger flexors. Scoring that resistance (ie, assigning an Ashworth score) can be heavily influenced by wrist position and elbow position. Many patients have little or no active finger extension, but some do. When the range of motion of passive finger extension exceeds active finger

20 874 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) extension or active extension is noticeably slower than active flexion, the possibility of extrinsic finger flexor co-contraction during active extension should be considered. An alternative possibility that might account for these findings is extensor muscle weakness. Muscles that potentially contribute to the clenched fist pattern include FDS and FDP. Both sets of extrinsic finger flexors can show varying degrees of volition, co-contraction, and spasticity. It is not unusual to find greater volitional control in some finger flexors and less control in others. Some studies have shown more volition in FDP muscles as a group than FDS muscles. Co-contraction in finger flexors might override and mask the patient s potential to extend the fingers. The authors have seen many patients who present with overactivity in just one or two muscle slips of FDP or FDS. For example, isolated index finger flexion deformity can result from co-contraction or dystonic overactivity in FDP or FDS muscle fascicles of that finger alone. These patients complain that their flexed index finger gets in the way of picking up objects with the radial side of the hand. Chemodenervation to index finger musculature alone is effective in relieving clinical dysfunction. Some degree of contracture of the extrinsics is typical of patients who have a chronically clenched fist. Passive rheologic properties of finger flexors (ie, their static physical stiffness) can also restrict active finger extension. Dynamic EMG studies performed with wires inserted separately into FDS, FDP, extensor digitorum communis (EDC), and lumbricales might help differentiate between muscle overactivity in FDS or FDP and muscle underactivity or weakness in EDC and lumbricales (a synergist of EDC during finger extension). The clenched fist deformity is amenable to treatment with chemodenervation and orthopedic lengthening (Table 6). The authors prefer not to use phenol in the depths of the forearm because it might leak onto nearby sensory nerve branches and cause dysasthesia. The intrinsics of the hand might be also be overactive, but an intrinsic plus posture (ie, MCP flexion combined with PIP extension) is not usually seen because overactive extrinsic flexors are strong enough to flex all joints; however, chemodenervation or surgical lengthening of extrinsics might unmask intrinsic overactivity, potentially converting a clenched fist deformity into an intrinsic plus deformity (Table 7). Chemodenervation with botulinum toxin is an excellent remedy for treating overactivity of the intrinsics because these small muscles of the hand are readily accessible for injection and require only small amounts of toxin to be effective. Thumb-in-palm deformity In patients who have the thumb-in-palm deformity, the thumb is pulled into the palm and is unable to extend during the reach phase of reaching to grasp an object. The thumb does not function well during handgrip and does not serve well as a post for the fingers. Clenched fingers often

21 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Table 6 Muscles that might exhibit overactivity in the clenched fist Muscles Typical overactivity Flexor digitorum sublimis Index +++ Long +++ Ring ++ Little + Flexor digitorum profundus Index ++ Long ++ Ring + Little 0 accompany a thumb-in-palm deformity. With respect to symptoms, patients complain of the disfiguring appearance of a thumb poking out between clenched long and ring fingers or buried in the palm underneath flexed fingers. Occasionally, a long thumbnail will dig into index finger skin painfully. With respect to passive function, donning a glove or a resting hand splint can be problematic, especially when thumb-in-palm is accompanied by a clenched fist. With respect to active function, thumb extension and abduction that open up the web space before grasp are compromised by the thumb-in-palm deformity. The thumb-in-palm deformity restrains activation of the commonest types of grasp patterns including three-jaw chuck, lateral grasp ( key pinch), and tip pinch. Physical examination reveals the typical resting position of the thumb in the palm. When the interphalangeal (IP) joint of the thumb is flexed but the carpometacarpophalngeal (CMC) joint is not, overactivity of flexor pollicis longus (FPL) is suspected. CMC joint flexion points to potential involvement of flexor pollicis brevis, and an adducted thumb suggests involvement of adductor pollicis and, perhaps, first dorsal interosseous. Because FPL crosses the wrist joint anterior to its axis of rotation, the wrist angle should be identified and controlled when the examiner performs passive stretching of flexor pollicis longus. It is desirable to test intrinsics of the thumb with the wrist flexed to minimize the contribution of the extrinsic FPL to testing of the thumb intrinsics. Skin contracture in the web space might also play a role in narrowing the opening of the hand during reaching. Muscles that potentially contribute to the thumb-in-palm deformity include flexor pollicis longus, flexor pollicis brevis, adductor pollicis, and first dorsal interosseous, which abducts and flexes the index finger, thereby Table 7 Muscles that might exhibit overactivity in the intrinsic plus hand Muscles Typical overactivity Interossei +++ Lumbricales +

22 876 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Table 8 Muscles that might exhibit overactivity in the thumb-in-palm deformity Muscle Typical overactivity Flexor pollicis longus +++ Flexor pollicis brevis + Adductor pollicis ++ First dorsal interosseous + narrowing the web space (Table 8). These thumb muscles are amenable to chemodenervation and orthopedic lengthening. The latter intervention is especially useful in younger individuals who have recovered a reasonable degree of motor control (as established by dynamic EMG studies) but are left with severe muscle and soft tissue contractures including skin and joint contractures. Flexed hip The patient who has a flexed hip presents with sustained hip flexion that interferes with positioning in a chair or wheelchair, sexuality, and gait. Chronic flexion posturing leads to flexion contracture. With respect to symptoms, hip flexor spasms are a common complaint of patients who have spinal cord lesions. With respect to passive function, hip flexion combined with adduction interferes with perineal care performed by caregivers. Sitting in a chair is altered by an excessively flexed hip and a patient might be more prone to ischial and sacra decubiti. With respect to mobility, excessive hip flexion during the stance phase of gait interferes with contralateral limb advancement and results in a shortened contralateral step. Patients who have muscle overactivity of the hip flexors bilaterally walk with a crouched gait pattern. The hips remain flexed throughout swing and stance. Crouching is particularly evident during mid to late stance, when the hip is extending. Overactivity of the hip flexors causing a crouched gait also leads to compensatory knee flexion to maintain balance. Crouched positioning demands high-energy consumption because it requires continuous use of quadriceps, hip extensors, and calf musculature to maintain upright balance against gravity. Few patients are able to remain long-term walkers with this deformity. Physical examination typically reveals a flexed hip posture with the thigh often adducted as well. Hip flexion contracture, which is often present, can be demonstrated by the Thomas test. Pelvic obliquity can occur when muscle overactivity in hip flexture and thigh adductors coexist. Muscles that potentially contribute to an excessively flexed hip include the iliopsoas, rectus femoris, and pectineus (Table 9). The adductor longus and brevis might also contribute to hip flexion. Dynamic EMG studies might be helpful in sorting out muscle overactivity in iliopsoas, rectus femoris, pectineus, and

23 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) Table 9 Muscles that might exhibit overactivity in the flexed hip Muscles Typical overactivity Iliopsoas +++ Rectus femoris ++ Pectineus + Adductor longus and brevis ++ adductors along with weakness of hip extensors and lumbar paraspinals. Overactivity in muscles relevant to the flexed hip deformity is amenable to chemodenervation, neurolysis, and orthopedic interventions. Adducted thigh The patient who has adductor muscle overactivity presents unilateral or bilateral scissoring thighs. Scissoring thighs interfere with perineal care, sexual intimacy, sitting, transfers, standing, and walking. With respect to symptoms, patients complain of stiffness. With respect to passive function, caregivers have difficulty providing perineal care, especially when there is bilateral scissoring associated with bilateral hip flexion posturing. Proper sitting position and posture is impeded. With respect to mobility, severe hip adduction interferes with limb clearance and advancement during the swing phase of gait. The base of support is narrow during the stance phase with potential impairment in balance that usually requires an upper extremity assistive device. Physical examination might suggest volitional capacity in the adductors and possible weakness in abductors. A relative leg length discrepancy might be associated with an adductor contracture or severe spasticity. In such a patient, measurements from the anterior superior iliac spine (ASIS) to the medial malleolus are similar for both lower limbs, but measurements from the umbilicus to the medial malleolus on each side are not. When the examiner attempts to perform passive abduction of the thigh in a patient who has adductor contracture or severe spasticity, the pelvis as a whole moves, the ASIS on the same side moves upward, and the pelvis appears to be oblique (ie, not parallel to the foot of the bed). A local anesthetic block to the obturator nerve helps reveal the presence or absence of contracture. Following an obturator block, the patient s base of support might widen and advancement of the swing limb might improve, suggesting that the scissoring deformity is dynamic. Unmasking voluntary hip abduction might also be revealed by a temporary obturator nerve block. Blocks might be useful in predicting longer-term responses to neurolysis or orthopedic surgery. Muscles that potentially contribute to these deformities include adductor longus and brevis, adductor magnus, gracilis, iliopsoas, and pectineus

24 878 N.H. Mayer, A. Esquenazi / Phys Med Rehabil Clin N Am 14 (2003) (Table 10). Gait analysis including kinematics and dynamic EMG can help identify and document the distribution of muscles with overactivity and underactivity and the degree of adduction present. For example, the adductors might provide compensatory function to advance the swing limb when hip flexors such as iliopsoas are weak. Under these circumstances, interventions aimed at modifying adductor activity need to be thought through carefully. When many muscles are involved in producing adduction deformity, neurolysis of the obturator nerve might be more efficient than chemodenervation (which also has a ceiling dose). Orthopedic interventions including transection of the anterior branch of the obturator nerve (for dynamic deformity) and proximal release of the adductors (for static contracture) are effective considerations. Stiff knee The stiff knee typically presents as a gait deviation with the knee remaining extended through most of the gait cycle. A stiff knee is particularly problematic during the preswing, initial swing and midswing subphases of the gait cycle. The limb becomes functionally longer and toe drag in early swing can cause tripping and falling. To achieve limb clearance of the floor during swing phase, the patient attempts to compensate for a relative increase in leg length by ipsilateral circumduction or hiking of the pelvis or by contralateral vaulting, often at the expense of increased energy consumption. On occasion, a stiff knee might fail to relax while the patient is seated and requires elevated leg rest support. Standing and transfers are problematic. From a perspective of muscle overactivity, muscles that potentially contribute to this UMN dysfunction include rectus femoris, vastus intermedius, vastus medialis and lateralis, gluteus maximus, and hamstrings (Table 11). Weakness in a number of muscles exacerbates the condition, including a weak iliopsoas and weak hamstrings. If ankle equinus with weak calf strength is also present, a weak plantar flexion moment in terminal stance results in further reduction of knee flexion. Gait laboratory studies including dynamic EMG recordings are helpful in identifying overactive and underactive muscles. If the quadriceps group is overactive during swing, the Table 10 Muscles that might exhibit overactivity in the adducted thigh Muscles Typical overactivity Adductor magnus +++ Adductor longus and brevis +++ Gracilic ++ Pectineus ++ Iliopsoas +