Clinical Learning Exercise #1 Exercise: We are going to assume nothing is wrong with the peripheral nervous system and attempt to identify the central nervous system anatomical location for the following examples. Please identify: (1) the anatomical location, (2) the side or sides of the brain involved, and (3) whether the anatomical site is firing too much or not enough. Example #1 A patient has lost his right arm swing Loss of arm swing is generally from lack of basal ganglia direct pathway activation to excite the thalamus in order for corticospinal projections from the motor cortex to activate the central pattern generators (CPGs). It is one of the earliest signs of basal ganglia direct pathway issues or lack of frontal cortex activation of the basal ganglia direct pathway on the contralateral side. Simply put, the contralateral frontal cortex motor regions activate the basal ganglia direct pathway, which excites the thalamus and winds up the motor cortex. This then activates corticospinal projections throughout the brainstem and spinal cord. In those regions, networks called central pattern generators produce rhythmic pattern outputs in the limbs, such as arm swing with ambulation. Decreased cortical activation of the frontal cortex and/or basal ganglia direct pathway leads to reduced arm swing on the contralateral side. Functional Neurology Seminars LP 2016 1
Example #2 A patient notices foul smells throughout his house and has increased episodes of déjà vu. Both phantom smells and episodes of déjà vu occur from spontaneous firing of neurons (epileptiform activity) in the temporal lobe. Phantom smells are the perception of odor, such as something burning, a rubber smell, or otherwise something usually foul. These are both common with temporal lobe epilepsy. The seizures may vary in intensity and quality. Example #3 An individual suffers from facial tics and jerks of his right shoulder. He can suppress them, but then he has an explosion of contracture. Tics are usually due to lack of basal ganglia indirect pathway inhibition, or gating, of the thalamus. Tics that involve the basal ganglia indirect pathway can be suppressed with focus from the frontal cortex for a short period of time, but that then leads to an inability to maintain suppression and then explosion of the tic response (vocal, motor, or both). Example #4 A person walking down the hallway has a subtle sway to the left. A subtle sway can involve the midline cerebellum. The midline cerebellum activates vestibulospinal pathways, which activate the intrinsic muscles of the spine and allow for proper load recover during natural titubations of the trunk during movement. When the midline cerebellum is not able to activate the intrinsic spinal muscles, they cannot prevent sway of the trunk during ambulation. This leads to a subtle sway towards the side of cerebellum involved during ambulation or during a Rhomberg s test. Functional Neurology Seminars LP 2016 2
A subtle sway may also occur from lack of somatosensory input to the contralateral parietal lobe. If a functioning parietal cortex is not able to integrate proper proprioceptive information from contralateral joints, ligaments, and muscle spindles, then inefficiency can be found with ambulation, causing a sway contralateral to the involved parietal cortex. Therefore, a sway to the left may involve the left midline cerebellum or the right parietal cortex. Further examination findings can help distinguish the involved region. Example #5 A person walking down the hallway has sudden symptoms of vertigo and falls to the left. A sway the left with symptoms of vertigo suggest increased activity of the vestibulocerebellum, not decreased. The key feature in this scenario is sudden symptoms of vertigo. Increased activation of the ipsilateral vestibulocerebellum activates extensors on the ipsilateral side and leads to sways and even to drop attacks. Example #6 A person has episodes of staring blankly without any response to the environment. He almost seems to be frozen for a few seconds. These are patterns associated with absence seizures that generally last a few seconds and are characterized by a blank or absent stare. An individual may have 10 100 absent seizures in a given day. They occur due to abnormal electrical activity throughout the entire brain. Example #7 A person has a spastic posture of elbow flexion, supination, and wrist flexion on the left. Functional Neurology Seminars LP 2016 3
Spastic posture is a key feature of injury to the motor cortex all the way down the corticospinal tract and crossing at the contralateral lower brainstem (medulla). An isolated spastic posture of elbow flexion, supination, and wrist flexion on the left suggests injury to the right precentral gyrus (frontal cortex) in the superior region, associated with the homunculus distribution of the arm the on the right. Example #9 A person feels sensations as if someone is touching the left side of their face and arm. This suggests spontaneous discharge of the post- central gyrus (somatosensory cortex) in the inferior regions associated with the homonuclus distribution of the face on the inferior region on the right side. Example #10 A person walks with a slight stooped posture and flings their arms all over the place. Hypotonia (lack of muscle tone) is a key feature of cerebellum impairment of the lateral cerebellum. Stooped posture is associated with midline cerebellum impairment. Bilateral involvement of the limbs flinging all over the place with a stooped posture represents compromise of the entire cerebellum, which is typically seen with metabolic injury to the cerebellum or from lack of cerebellum development. Example #11 A person has sudden uncontrollable jerking of his right leg. Sudden, explosive, and uncontrollable jerks are myoclonic movements and reflect spontaneous discharge of the motor cortex. Myoclonic jerks involving the right leg suggest involvement of the left motor cortex in the homunculus distribution of the leg parasagittally. Functional Neurology Seminars LP 2016 4
Example #12 A person has episodes of uncontrollable crying and laughing without any emotional trigger. Episodes of uncontrollable crying and laughing involve spontaneous discharge of the limbic (emotional) regions of the brain. These typically occur from failure of the basal ganglia indirect pathway of the limbic loop. In these cases, impairment in the basal ganglia cannot dampen, or gate, thalamic projections into the limbic regions. Example #13 A person feels nausea when watching a movie that takes place on a boat in the middle of the ocean. Discharge into the vagal nuclei can induce symptoms of nausea. When movement or perception of movement induces nausea, it suggests involvement of the cerebellum purkinje inhibition system. Lack of activation of the purkinje cells lead to impaired suppression, or gating, of cerebellum outward projections to the pontine vagal centers. This causes symptoms of nausea with motion. You can identify which side is involved by turning the head to the right or left while watching the movie. The side of the head turn that increases nausea symptoms is usually the involved side. Example #14 A person notices during yoga class they cannot balance on their left leg very well. Lack of balance suggests involvement of the vestibulocerbellum. The side of involvement is ipsilateral to the side of impaired balance. In this case, lack of left leg balance suggests lack of activity of the left vestibulocerebelum. Functional Neurology Seminars LP 2016 5
Example #15 A person has bumps and bruises all over the left side of his body. He recently got in a car accident while pulling out into traffic from being parked at the curb. Somatosensory perception and visual neglect on the left side of the body suggest impairment of the right parietal cortex. Example #16 A person has difficulty articulating words when speaking. The motor function of speech (articulation) involves the left cortex (the dominant language hemisphere in 97 percent of individuals) in the left inferior frontal region, called Broca s area. Example #17 A person keeps judging distance inappropriately when reaching out for objects. Inaccuracies in reaching for objects is termed optic ataxia and involves the contralateral posterior parietal/occipital integration regions of the brain. Example #18 A person notices tinnitus bilaterally, but with greater ringing perception in the right ear. This may indicate spontaneous discharge involving the auditory cortex in the superior temporal lobe. Greater perception of hearing in the right ear suggests involvement of the left superior temporal lobe. Functional Neurology Seminars LP 2016 6
Example #19 A person finds pinprick sensations with pinwheel stroking is very painful on the right side of the leg and foot. Increased perception of pinprick on the right leg or foot suggests neurons closer to threshold on the contralateral parietal cortex (somatosensory cortex) in the parasagittal region associated with the right foot and leg. It can also suggest lack of descending pain inhibition pathways from the periaqueductal gray on the ipsilateral side of the pinprick sensation. It may also suggest lack of hypothalamospinal inhibition of the interomediolateral cell column involved with dampening sympathetic response ipsilateral to the pinprick. Example #20 A musician has great sense of beat and tempo but cannot hear lyrics unless there is no background music. The inability to perceive lyrics with background music suggests lack of integration in the auditory cortex. Beat and tempo have a stronger interpretation with left auditory cortex while lyrics have a stronger perception of the right auditory cortex. This case suggests lack of integration of the right auditory cortex (superior temporal cortex) due to difficulty hearing lyrics only with background music. Example # 21 A person complains they have difficulty with focus, concentration, and remembering what they just learned. Focus, concentration, and working memory (short- term) memory involves the prefrontal cortex. It is difficult to identify the involved side with this complaint alone. Functional Neurology Seminars LP 2016 7
Example #22 A person is starting to notice impairments in recall and longterm memory. Long- term memory (declarative memory) involves the medial temporal lobe region called the hippocampus. Difficulty with word and letter recall involves the left side. Difficulty with spatial recall involves the right side. Example #23 A person has right-left confusion. Left- right confusion is a key feature of the left parietal cortex. Example #24 A person hears voices and sounds that are not there. This suggests spontaneous firing of the auditory cortex (superior temporal lobe), typically involving temporal lob seizures. Example #25 An individual is unable to find locations when driving without using a navigation system. This involves the hippocampus or the medial temporal lobe, typically on the right side. It is a common feature of early dementia. Functional Neurology Seminars LP 2016 8
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