HOW TO GET THE MOST OUT OF NERVE CONDUCTION STUDIES AND ELECTROMYOGRAPHY

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1 HOW TO GET THE MOST OUT OF NERVE CONDUCTION STUDIES AND ELECTROMYOGRAPHY W G Fuller J Neurol Neurosurg Psyhiatry 2005; 76(Suppl II):ii41 ii46. doi: /jnnp hy should we think hard when requesting nerve ondution studies (NCS) and eletromyography (EMG)? Aside from the reasons that should determine our use of all investigations there are two partiular issues that relate to these tests: NCS/EMG is at best unomfortable, at worst painful, for the patient despite the neurophysiologist s best efforts NCS/EMG are expensive, although this ost is borne by the health are system. They take minutes of a neurophysiologist s time, a sare and expensive resoure. ELECTRODIAGNOSTIC STUDIES ARE AN EXTENSION OF CLINICAL EXAMINATION Very early on in just about every textbook or artile on NCS/EMG the following two observations are made: The tests do not replae a areful history and examination of the patient NCS/EMG are an extension of the linial assessment. These observations may seem implausible to those who do not perform these tests and view eletrodiagnosti tests as a blak box from whih answers magially appear. However, neurophysiology is very definitely used in the same way as linial examination to solve linial problems, and omplements the linial evaluation rather than replaing it. In linial examination you determine the site of the lesion by assessing the distribution of weakness, reflex hanges, and sensory loss. Neurophysiologially you not only examine the distribution but also the type of abnormalities deteted in the nerve ondution studies and EMG. Neurophysiology an be thought of as the linial examination with the ability to probe nerves and musles in a different manner. There are a few obvious parallels with linial examination: It is usually more straightforward to loalise a signifiant weakness linially than a milder degree of weakness where you tend to be less ertain in distinguishing mild weakness from normal strength. Similarly soft sensory signs tend to be more diffiult to loalise. These same problems arise neurophysiologially a more signifiant lesion is easier to loalise as the neurophysiologial abnormalities are more lear ut. If it is diffiult to obtain ooperation in the linial examination it is likely to be more so when doing neurophysiology espeially EMG whih requires a high level of patient ooperation. When examining a patient you are often able to disount ertain linial findings that relate to known prior pathology for example, a mild foot drop from a previous L5 radiulopathy; the neurophysiologist has to do the same so please tell them about it. NCS/EMG and linial examination are both operator dependant. NCS/EMG is partiularly helpful in loalising a peripheral nervous system defiit found on linial examination. Thus: If you annot frame your question in anatomial terms, whih is how the neurophysiologist will try to answer it, then wonder why you are ordering the test at all. If you an loalise the lesion with onfidene on linial examination alone, will you gain additional useful information from requesting NCS/EMG? Often neurophysiologial studies an determine the site of the lesion more preisely than examination alone, but they do not determine the ause. Usually this will require other investigations and it may be that the neurophysiologial studies add nothing to the diagnosis if these other tests are diagnostially positive. For example, neurophysiologial onfirmation of an L5 radiulopathy may ontribute little if the magneti resonane image (MRI) of the lumbosaral spine learly demonstrates an L5 root ompression. If you are going to do other tests, onsider Correspondene to: whether NCS/EMG will add to the diagnosis. In the era of the programmed investigation Dr Geraint Fuller, Department of Neurology, Glouester approah remember that blok booking tests and thus failing to appreiate the value of an Royal Hospital, Great Western investigative pathway is a poor rather than effiient use of diagnosti resoures. Road, Glouester GL1 3NN, Before onsidering the role NCS/EMG play in different linial situations it is worthwhile UK; geraint@fullerg.demon. o.uk onsidering a little about the tests themselves and making some observations about how we use investigations in general. ii41 J Neurol Neurosurg Psyhiatry: first published as /jnnp on 16 June Downloaded from on 29 September 2018 by guest. Proteted by opyright.

2 ii42 TESTING THE TESTS Evidene based mediine suggests that we should understand the partiular features of diagnosti tests, suh as the sensitivity (the ability to detet those with disease) and speifiity (the ability to detet those without). To alulate these we require the test to be ompared to an aepted gold standard. This leads to the first problem for NCS/EMG. For some onditions for example, hroni inflammatory demyelinating polyradiulopathy (CIDP) or multifoal motor neuropathy with ondution blok NCS/EMG is an essential part of definition of these onditions making sensitivity and speifiity alulations somewhat irular, though attempts are made to assess different sets of diagnosti riteria. 1 For other onditions, suh as arpal tunnel 2 or ulnar neuropathy in the ubital tunnel, 3 while NCS/EMG are not the only way of onfirming the diagnosis, they are probably the most robust non-invasive method. In other situations another modality an provide a more definitive diagnosis for example, ervial radiulopathies where MRI or surgial findings an provide the gold standard. 4 Paradoxially, this means that the onditions where there is the best published evidene on sensitivity and speifiity are those where there is another more definitive method of ahieving a diagnosis, this being used as the gold standard against whih NCS/EMG an be ompared. Cervial and lumbar radiulopathy are lear examples of this. The next problem is that NCS/EMG is not a single investigation but an evolutionary one in whih a series of tests an be applied to a linial problem. The tests that are used will be ditated by the linial presentation but also are adjusted aording to the results of the other tests as the examination proeeds. Thus a patient referred with possible ulnar nerve lesion with weakness and wasting in the first dorsal interosseous and found to have normal ulnar motor and sensory studies prompts a searh for dennervation in other T1 musles, and next a more widespread searh of dennervation that might suggest anterior horn ell disease. As an be readily appreiated, this means that the tests are signifiantly operator dependant, partiularly the EMG element of the examination. This proess of ongoing detetion reflets the skill and expertise of the operator, partiularly in the assessment of more omplex linial problems. While quantitative EMG is being used more extensively, most EMG assessments depend on a large element of judgement on the part of the neurophysiologist. NCS/EMG are not just normal or abnormal, there is a signifiant range of normality, whih an be wide for some measures. Also there are different degrees of abnormality, from something that just falls outside the normal range, to the lear ut. Generally this will produe diffiulties when defiits are subtle. Some examples: the absene of a medial plantar sensory response an be taken as an indiation of a neuropathy but this is also absent in 8% of normal subjets 5 finding fibrillation potentials in the small musles of the feet an be interpreted as indiating a length dependant motor neuropathy but are found in 20% of normal subjets. 6 As an be appreiated, the speifiity and positive preditive value of a very lear ut abnormality is muh greater than for a milder one. By analogy, a haemoglobin onentration of 5 g/dl is lear evidene of anaemia, while a Box 1 An illustration of how the prevalene of the ondition being tested for profoundly alters the way results should be interpreted. The same test, test A for ondition X, whih has a sensitivity of 85% and speifiity of 97%, is used in three different populations. Population 1: sreening of general population: prevalene of ondition X is 3% 300 in tests: Has ondition X (300) Test positive Test negative Positive preditive value = 47% Negative preditive value = 99% Does not have ondition X (9700) Despite this being a test with high speifiity in this population less than half those with a positive test have ondition X. Population 2: testing in a population with symptoms suggestive of the ondition drawn from the general population: Prevalene of ondition X is 20% in this population 40 in 200. Has ondition X (40) Test positive 34 5 Test negative Positive preditive value = 87%. Negative preditive value = 96%. Does not have ondition X (160) In this setting with a higher prevalene of the ondition the test is muh more useful though there are still a signifiant number of false positives and false negatives whih might result in 1 in 6 operations being unneessary. Population 3: diagnosti testing in a patient thought to be quite likely to have the ondition: prevalene of ondition X is 50% 100 in tests: Has ondition X (100) Test positive 85 3 Test negative Positive preditive value = 97% Negative preditive value = 86% Does not have ondition X (100) With a high linial likelihood this test is very helpful. Same test, different setting, very different results. Test A is omparison of median and ulnar sensory lateny from ring finger (AAN pratie parameters). Condition X is arpal tunnel syndrome. The prevalenes given are those of general population, 13 population of symptomati patients from general population, 13 and a hypothetial situation with a pre-test probability of 50%. J Neurol Neurosurg Psyhiatry: first published as /jnnp on 16 June Downloaded from on 29 September 2018 by guest. Proteted by opyright.

3 Table 1 Nerve Methods used in loalising upper limb foal mononeuropathies Site of lesion Demonstration of foal slowing haemoglobin of 10.9 g/dl falls outside the normal range but its linial signifiane is less ertain. This question of ertainty has perhaps been best explored in relation to arpal tunnel syndrome. 7 The signifiane of a test result will also vary depending on how likely it is that a patient has the ondition being tested for. This an be easily illustrated by onsidering the impat of using a sensitive test, whih is also reasonably speifi, in populations with different prevalenes of the ondition being tested for (box 1). While this is easy to understand when applied to a population, the same applies when you onsider the pre-test probability of having a diagnosis on linial grounds a pre-test probability of 20% equates to a population prevalene of 20%. A test is muh more useful in patients who are likely to have the ondition being tested for if they are unlikely to have the ondition the number of false positive results will lead to inappropriate diagnoses and investigations. It is also important to onsider whether the degree of abnormality found is onsistent with the linial piture. Using the anaemia analogy again, haemoglobin of 5 g/dl is a reasonable explanation for lethargy and fatigue, while haemoglobin of 10.9 g/dl is probably not. PRAGMATIST OR COMPLETIST A test should not be onsidered in isolation. We must also onsider where it fits into the best diagnosti strategy the strategy by whih you get to the diagnosis and make the best management deisions as effiiently and effetively as possible. This involves thinking not only about the test in question but also other investigations and the potential therapeuti and prognosti impliations of the results of these investigations. Most researh is foused on partiular tests and there is less researh into the effetiveness of diagnosti strategies, something most liniians develop through linial pratie, though studies in this are beginning to appear. 8 9 Neurologists fall into a spetrum that an be haraterised as running from extreme pragmatists, whose objetive is to do as few investigations as possible, preferably none, to solve the immediate linial management problem, to extreme ompletists, who wish to eliminate every possibility, Finding hanges in CMAP and SAP Dennervation hanges in nerve distribution Comments Common Median Carpal tunnel EMG not usually needed Ulnar Elbow (ubital tunnel) Unommon Radial Upper arm Axillary Humeral head NA NA ++ Ulnar Wrist (Guyon s anal) or hand Depends on other ulnar studies being normal Long thorai Not lear NA NA ++ Limited usefulness; small risk of pneumothorax Rare Anterior interosseous branh of median nerve Just below the elbow NA NA ++ Depends on other median studies being normal Posterior interosseous branh of radial nerve As nerve enters supinator musle NA NA ++ Depends on other radial nerve studies being normal Suprasapular Suprasapular noth NA Musuloutaneous NA high likelihood; ++ probable finding; + possible finding; unlikely finding. Findings will be dependant on severity of lesion. CMAP, ompound motor ation potential; NA, not appliable; SAP, sensory ation potential. however remote, and doument every defiit as ompletely as possible, even when this has no immediate therapeuti impliations. Most neurologists lie somewhere in between, and reflet their role. Tertiary entre neurologists are probably more ompletist, while those in seondary entres are more likely to be pragmatists. Other fators suh as the ulture they work in, subspeialisation, medio-legal experienes, and their own personality will influene their approah. The pragmatist will develop a strategy that uses tests that provide unique and definitive information. The ompletists will use investigations to build up and doument the ondition. Both will run into different problems: The pragmatist is at risk of misdiagnosing onditions, partiularly those that are rare and mimi a more ommon alternative. The ompletist is at risk of misdiagnosing onditions beause they may be misled by false positive results, partiularly when using tests in situations where there is a low prevalene of the ondition in question (true positives). You will appreiate this spetrum of approah informs on the uptake of NCS/EMG that we now onsider in ertain linial settings. LEVEL OF THE PERIPHERAL NERVOUS SYSTEM Foal mononeuropathies Requests for studies in patients with suspeted foal mononeuropathies are a ommon reason for referral for neurophysiology, and of these arpal tunnel syndrome and ulnar mononeuropathies are the most ommon. Neurophysiologial studies may be able to demonstrate an abnormality in the nerve, the site of involvement either: diretly, if the site of involvement is anatomially loated, to allow diret study of the nerve at that site, or by inferene, if no diret study of the nerve at that site is possible, but hanges onsequent on the lesion, either hanges in motor or sensory responses or dennervation hanges, lead to the dedution of the lowest possible site of involvement. They also determine whether there is evidene of more widespread sublinial peripheral nerve abnormalities. ii43 J Neurol Neurosurg Psyhiatry: first published as /jnnp on 16 June Downloaded from on 29 September 2018 by guest. Proteted by opyright.

4 ii44 They an be helpful for: Diagnosis if you are unsure of the loalisation on linial grounds. Management if you are onsidering surgial deompression then the most aurate loalisation possible is desirable. Generally it would seem prudent to undertake a non-invasive test to doument a foal neuropathy before an invasive proedure even if the diagnosis is seure on linial grounds. Prognosis if you wish to determine the degree of peripheral nerve damage. This will tend to be helpful in patients with a more severe peripheral nerve lesion usually of more sudden onset, for example, trauma or ompression and distinguish between neuropraxia and axonotmesis as well as those situations where the nerve is no longer in ontinuity. Often this distintion annot be made autely, when the distintion would be most helpful. If there is real onern the nerve may not be in ontinuity, surgial exploration may be needed. Tables 1 and 2 give a list of ommon mononeuropathies indiating how eletrodiagnosti studies loalise different foal neuropathies. Those where foal abnormality an be diretly demonstrated provide the greatest diagnosti auray and diagnosti ertainty. Those nerves where there are hanges in the motor responses and on EMG provide a lower level of diagnosti onfidene and loalisation, and those with EMG hanges alone lower still. RADICULOPATHIES In the majority of patients with symptoms or signs of a ervial or lumbosaral radiulopathy the diagnosti issue is whether there is radiular ompression, usually related to dis disease, and the subsequent management revolves around the role of surgery. For suh patients imaging, in partiular MRI, is the most effiient investigation. In the past, when myelography was the imaging modality of hoie, neurophysiologial investigations were important in seleting patients for whom the small risks of ontrast myelography Table 2 Nerve Methods used in loalising lower limb foal mononeuropathies Common Lateral utaneous nerve of the thigh Site of lesion Demonstration of foal slowing were worth taking. However, the low risk of spinal MRI has hanged this and the role for neurophysiology is redued. Diagnosis of a radiulopathy with eletrodiagnosti studies depends on there being an axonal motor defiit suffiient to produe dennervation hanges that EMG an detet in musles within a speifi myotome. Loalisation with EMG an identify the myotome involved; however, the spinal level at whih the nerve root involved exits the spinal anal is less ertain as nerve roots ommonly exit the spinal anal a level above (pre-fixed) or below (post-fixed) the expeted spinal level. In the small number of patients where imaging is equivoal, neurophysiology may be valuable in distinguishing radiulopathies from plexopathies. However, for both radiulopathies and plexopathies the loalisation of the lesion does not provide an aetiologial explanation for the defiit this will only be provided by other fators, suh as the time ourse, further imaging, or other investigative findings. Plexopathies Neurophysiologial studies of plexopathies an demonstrate the distribution and severity of any dennervation, with involvement of musles beyond the distribution of single nerve roots. Here the neurophysiologists must have a detailed knowledge of neuroanatomy to interpret these loalising findings. There may be abnormalities of sensory responses as plexus lesions are post-ganglioni. EMG of paraspinal musles should be normal as these are innervated by posterior nerve roots originating proximal to the plexus. As you will appreiate these studies an support the plexus as the site of the lesion but again do not provide an aetiologial diagnosis. However, there are traps, partiularly if the lesion is mild. Absene of involvement of paraspinal musles does not exlude a radiulopathy. Not all plexus lesions will lead to hanges in those sensory responses that are aessible to measurement. If you remain in doubt then alternate diagnoses need to be exluded by other modalities, partiularly multiple radiulopathies with MRI. Finding hanges in CMAP and SAP Dennervation hanges in nerve distribution Comments Inguinal ligament NA NA Eletrodiagnosti studies limited in this ommon mononeuropathy Common peroneal Fibular head Interdigital Between heads of NA NA Diffiult nerves to study metatarsals Unommon Femoral NA NA +++ Distinguish from plexopathy/ radiulopathy Siati Pelvis, buttok or thigh NA Tibial, at ankle Tarsal tunnel Perineal Alok s anal NA NA NA Saphenous Thigh or knee NA + NA Rare Tibial, at knee NA Posterior utaneous nerve of NA NA NA Limited use the thigh Obturator Obturator foramen NA NA ++ Gluteal NA NA ++ Sural NA +++ NA +++ high likelihood; ++ probable finding; + possible finding; unlikely finding. Findings will be dependant on severity of lesion. CMAP, ompound motor ation potential; NA, not appliable; SAP, sensory ation potential. J Neurol Neurosurg Psyhiatry: first published as /jnnp on 16 June Downloaded from on 29 September 2018 by guest. Proteted by opyright.

5 Peripheral neuropathies Nerve ondution studies an ategorise neuropathies aording to distribution (generalised or multifoal, or mono-neuritis multiplex), if they are sensory, sensorimotor or motor, and whether they are axonal or demyelinating. Studies may, however, be normal in small fibre neuropathies. There are many aetiologies to neuropathies and these differ aording to their varying neurophysiologial findings. One approah desribed in an exellent review 10 is to use NCS/ EMG as the primary method of lassifiation of a patient suspeted of having a neuropathy. From an epidemiologial point of view this means that the majority of patients tested will have a distal symmetrial axonal polyneuropathy, most assoiated with diabetes or alohol, where the diagnosis is straightforward. 11 An alternative strategy is to fous on what additional information the NCS/EMG provide and reognise that for many patients with a typial hroni neuropathy other fators, suh as diabetes, history of alohol or drug exposure lead to the diagnosis and the NCS/EMG adds nothing to the linial assessment. A study of this strategy found half of neurophysiologial studies performed added nothing to the eventual diagnosis in the investigation of patients with a distal symmetrial polyneuropathy of more than six weeks duration. 8 This study also reassuringly found that those patients with demyelinating neuropathies were reognised on linial grounds. If the role of nerve ondution studies and EMG in hroni neuropathies is disputed there is no suh ontroversy in their use in aute neuropathies, asymmetrial or multifoal neuropathies, or in any severe disabling neuropathy. Here the differential diagnosis inludes aute and hroni demyelinating polyneuropathies, and vasuliti neuropathies where eletrodiagnosti tests lead either to a diagnosis and treatment or strengthen the indiation for nerve biopsy. Any patient with a neuropathy that is not entirely typial for the putative ause should also be onsidered for neurophysiologial assessment. For the most part hanges in nerve ondution studies and EMG lead to a lear ategorisation of neuropathy. However, there are potential traps: As the fibres tested are large myelinated fibres a small fibre neuropathy may not be assoiated with hanges and other diagnosti tests suh as thermal thresholds may help. In patients with demyelinating neuropathy (for example, early Guillain-Barré syndrome) investigated early in disease ourse, hanges an be relatively subtle or absent. Anterior horn ell disease Neurophysiology serves two purposes in anterior horn ell disease. Firstly, it douments that the defiit relates to the anterior horn ell by demonstrating dennervation hanges with normal motor ondution and normal sensory studies, and eliminates alternative purely lower motor disorders, in partiular multifoal motor neuropathy with ondution blok. Seondly it an demonstrate evidene of dennervation in linially normal musles and by demonstrating a wider distribution of lower motor neurone abnormalities so orroborate the diagnosis of amyotrophi lateral slerosis (ALS). 12 Thus in a patient with disease limited to one body region or with a purely lower motor presentation, neurophysiology has the potential for substantially altering patient management. Nerve ondution studies (NCS) and eletromyography (EMG): key points The tests are there to help you (and if they won t help don t do them) NCS and EMG are an extension of linial examination. Generally NCS and EMG are effetive at loalising the level of the nervous system involved or the site of the lesion but not the ause Sometimes NCS an be misleading for example, finding abnormalities that our within the general population or misattributing myopathi and neuropathi weakness Tests other than NCS or EMG will usually be needed to determine the ause of a problem In a patient with evidene of widespread upper and lower motor neurone signs the study will simply doument the defiit and onfirm the linial diagnosis. Neuromusular juntion disorders Neurophysiology has been pivotal in defining disorders of the neuromusular juntion and is the test that haraterises these onditions. The investigations are straightforward in situations where the linial diagnosis is obvious but beome inreasingly diffiult in patients with more subtle or limited problems. The role of neurophysiology will vary. In a patient with lear linial evidene of myasthenia and a positive antiaetylholine reeptor antibody, repetitive nerve stimulation or single fibre may orroborate though would not exlude the diagnosis if normal. However, in a patient with a suggestive linial piture but a negative antibody test then neurophysiology may diagnosti. The pragmatist might argue the studies add nothing in the first situation and are thus unneessary. Neurophysiology provides the definitive diagnosis for patients with Lambert-Eaton myastheni syndrome (LEMS). Nerve ondution studies and EMG are helpful in distinguishing botulism from an aute demyelinating neuropathy. Musle disease Eletrodiagnosti studies an find evidene of a myopathy, eliminating alternative diagnoses, and doument the distribution of myopathi hanges. Some findings an point to speifi diagnoses for example, fibrillations suggesting an inflammatory myopathy, myotonia suggesting a myotoni disorder though for all these onditions other tests provide the gold standard for diagnosis. How should neurophysiology fit into the diagnosti strategy for a patient with a suspeted myopathy? Pragmatists would argue that a patient with the linial features of an inherited musle disorder for whih there is a simple geneti test, suh as myotoni dystrophy or fasiosapulohumeral musular dystrophy, should have appropriate geneti studies as neurophysiology would add nothing if the linial diagnosis is onfirmed though may be useful if it is not. Likewise if a patient has features of an inflammatory myopathy with raised inflammatory markers and raised reatine kinase in whom a musle biopsy will provide the definitive diagnosis, then this is the test that should be done. Neurophysiology is likely to be partiularly helpful if you are unsure whether the weakness is neurogeni (inreased amplitude, inreased duration units, with fewer units firing ii45 J Neurol Neurosurg Psyhiatry: first published as /jnnp on 16 June Downloaded from on 29 September 2018 by guest. Proteted by opyright.

6 ii46 at a high rate), or myopathi (short duration, small units with early reruitment to a full interferene pattern of redued amplitude) and thus will diret your diagnosti strategy. However, the distintion is not always lear ut and there are traps: Low amplitude polyphasi short duration motor units, normally indiative of a myopathi abnormality, an our in early reinnervation following dennervation. In severe myopathies loss of whole motor units an lead to limited reruitment mimiking a neuropathi lesion. Longer duration motor units, normally a feature of a neuropathi weakness, an be seen in myopathies with regeneration. Thus there is a risk that EMG an misattribute the level of weakness, espeially if the results are taken in isolation and the possibility of this misattribution is not onsidered. If the EMG result is at odds with other elements of the linial piture then think again. Syndrome hunting Sometimes NCS/EMG an be helpful in the differential diagnosis of patients who present with a more ompliated widespread neurologial problem. They an provide objetive evidene of involvement of peripheral nerve or musle in a patient with a predominantly upper motor neurone defiit or even dementia, whih hanges the differential diagnosis. For example, finding of widespread dennervation in a patient with upper motor neurone syndrome without sensory loss or in a patient with fronto-temporal dementia an lead to a diagnosis of motor neurone disease. RECOMMENDED READING Kimura J. Eletrodiagnosis in diseases of nerve and musle, 3rd ed. Oxford University Press A magisterial overview of peripheral neurophysiology. Staal A, van Gijn J, Spaans F. Mononeuropathies; examination, diagnosis and treatment. London: WB Saunders, An exellent and very aessible text on mononeuropathies. REFERENCES 1 Haq UR, Fries TJ, Pendelbury WW, et al. Chroni inflammatory demyelinating polyradiuloneuropathy; a study of proposed eletrodiagnosti and histologi riteria. Arh Neurol 2000;57: Jaleki CK, Andary MT, Floeter MK, et al. Pratie parameter: eletrodiagnosti studies in arpal tunnel syndrome. Neurology 2002;58: Amerian Assoiation of Eletrodiagnosti Mediine, Amerian Aademy of Neurology, Amerian Aademy of Physial Mediine and Rehabilitation. Pratie parameter for eletrodiagnosti studies in ulnar neuropathy at the elbow: summary statement. Musle Nerve 1999;22: Levin KH, Maggiano HJ, Wilbourn AJ. Cervial radiulopathies: omparison of surgial and EMG loalisation of single root lesions. Neurology 1996;46: Antunes AC, Nobrega JAM, Manzano GM. Nerve ondution study of the median and lateral plantar nerves. Musle Nerve 2000;40: Boon AJ, Harper CM. Needle EMG of abdutor halluis and peroneus tertius in normal subjets. Musle Nerve 2003;27: Nodera H, Herrmann DN, Holloway RG, et al. A Bayesian argument against rigid ut-offs in eletrodiagnosis of median neuropathy at the wrist. Neurology 2003;60: Rosenberg HR, Portegies P, de Visser M, et al. Diagnosti investigation of patients with hroni polyneuropathy: evaluation of a linial guideline. J Neurol Neurosurg Psyhiatry 2001;71: Haig AJ, Huey-Ming T, LeBrek DB. The value of eletrodiagnosti onsultation for patients with upper extremity nerve omplaints: a prospetive omparison with history and physial examination. Arh Phys Med Rehabil 1999;80: England JD, Asbury AK. Peripheral neuropathy. Lanet 2004;363: MaDonand BK, Cokerell OC, Sander JWAS, et al. The inidene and lifetime prevalene of neurologial disorders in a prospetive ommunity based study in the UK. Brain 2000;123: Brooks BR. El Esorial World Federation of Neurology riteria for the diagnosis of amyotrophi lateral slerosis. Subommittee on motor neuron diseases/amyotrophi lateral slerosis of the World Federation of Neurology Researh Group on Neuromusular Diseases and the El Esorial Clinial limits of amyotrophi lateral slerosis workshop ontributors. J Neurol Si 1994;124(suppl): Atroshi I, Gummesson C, Johnsson R, et al. Prevalene of arpal tunnel syndrome in a general population. JAMA 1999;282: EEG HAPPY FAMILIES... Answers EEG number Request form Tehniian s report Conlusion 1 B iv f 2 C v a 3 D i g 4 E ii h 5 F iii d 6 A vii 7 G viii e J Neurol Neurosurg Psyhiatry: first published as /jnnp on 16 June Downloaded from on 29 September 2018 by guest. Proteted by opyright.