Electrophysiological evaluation of conduction in the most proximal motor root segment

Normal Values of Central, Peripheral, and Root Motor Conduction Times in a Healthy Korean Population

PURPOSE

Central, peripheral, and root motor conduction times (CMCTs, PMCTs, and RMCTs, respectively) are valuable diagnostic tools for spinal cord and motor nerve root lesions. We investigated the normal values and the effects of age and height on each motor conduction time.

METHODS

This study included 190 healthy Korean subjects who underwent magnetic stimulation of the cortex and spinous processes at the C7 and L1 levels. Recording muscles were abductor pollicis brevis and abductor digiti minimi in the unilateral upper limb and extensor digitorum brevis and abductor hallucis in the contralateral lower limb. F-wave and compound motor nerve action potentials were also recorded. Central motor conduction time was evaluated as the difference between cortical motor evoked potential onset latency and PMCT using calculation and spinal stimulation methods. Root motor conduction time was computed as the difference between spinal stimulated and calculated CMCTs.

RESULTS

The average age and height of the participants were 41.21 ± 14.39 years and 164.64 ± 8.27 cm, respectively; 39.5% (75/190) patients were men. In the linear regression analyses, upper limb CMCTs showed a significant and weak positive relationship with height. Lower limb CMCTs demonstrated a significant and weak positive relationship with age and height. Peripheral motor conduction times were significantly and positively correlated with age and height. Root motor conduction times showed no significant relationship with age and height, except for abductor pollicis brevis-RMCT, which had a weak negative correlation with height.

CONCLUSIONS

This study provides normal values of CMCTs, PMCTs, and RCMTs, which have potential clinical applications. When interpreting CMCTs, age and height should be considered.

Detection of C8/T1 radiculopathy by measuring the root motor conduction time

BACKGROUND

Root motor conduction time (RMCT) can noninvasively evaluate the status of the proximal root segment. However, its clinical application remains limited, and wider studies regarding its use are scarce. We aimed to investigate the association between C8/T1 level radiculopathy and RMCT.

METHODS

This was a retrospective cross-sectional study. Subjects were extracted from a general hospital's spine clinic database. A total of 48 C8/T1 root lesions from 37 patients were included, and 48 C8/T1 root levels from control subjects were matched for age, sex, and height. RMCT was measured in the abductor pollicis brevis muscle and the assessment of any delays owing to C8/T1 radiculopathy.

RESULTS

The RMCT of the C8/T1 radiculopathy group was 1.7 ± 0.6 ms, which was significantly longer than that in the control group (1.2 ± 0.8 ms; p = 0.001). The delayed RMCT was independently associated with radiculopathy (adjusted odds ratio, 1.15; 95% confidence interval, 1.06-1.27; p = 0.011) after adjusting for the peripheral motor conduction time, amplitude of median compound motor nerve action potential, and shortest F-wave latency. The area under the Receiver Operating Characteristic curve for diagnosing C8/T1 radiculopathy using RMCT was 0.72 (0.61-0.82). The RMCT was significantly correlated with symptom duration (coefficient = 0.58; p < 0.001) but was not associated with the degree of arm pain.

CONCLUSION

Our findings illustrate the clinical applicability of the RMCT by demonstrating its utility in diagnosing radiculopathy at certain spinal levels.

Excitatory and inhibitory responses to cervical root magnetic stimulation in healthy subjects

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We studied excitatory and inhibitory responses to cervical root magnetic stimulation.

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CRMS elicited direct and reflex responses in hand muscles.

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CRMS is painless and well tolerated and, therefore, applicable to clinical studies.

Objectives

To characterize direct and reflex hand muscle responses to cervical root magnetic stimulation (CRMS) in healthy volunteers during sustained voluntary contraction.

Methods

In 18 healthy volunteers, we recorded from the first dorsal interosseous (FDI) muscle the responses to CRMS of progressively increasing intensity and level of muscle contraction. The compound muscle action potential (CMAP) and the silent period (SP) were compared to those obtained with plexus, midarm and wrist stimulation. Additionally, in a smaller number of subjects, we obtained the peristimulus time histogram (psth) of single motor unit firing in the FDI, examined the effects of vibration and recorded the modulation of sustained EMG activity in muscles of the lower limbs.

Results

Increasing CRMS intensity led to larger CMAP with no relevant changes in SP1 or SP2, except for lower amplitude of the burst interrupting the silent period (BISP). Increasing the level of muscle contraction led to reduced CMAP, shorter SP duration and increased BISP amplitude. The psth analysis showed the underlying changes in the motor unit firing frequency that corresponded to the changes seen in the CMAP and the SP with surface recordings. Progressively distal stimulation led to CMAPs of shorter latency and increased amplitude, SPs of longer latency and shorter duration, and a BISP of longer latency. Vibration led to reduction of the SP. CRMS induced SPs in muscles of the lower limb.

Conclusions

CRMS induces excitatory and inhibitory responses in hand muscles, fitting with the expected behavior of mixed nerve stimulation at very proximal sites.

Significance

Characterization of the effects of CRMS on hand muscles is of physiological and potentially clinical applicability, as it is a painless and reliable procedure.

Diagnosing chronic inflammatory demyelinating polyradiculoneuropathy with triple stimulation technique

OBJECTIVE

To assess the value of triple stimulation technique (TST) for diagnose of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).

METHODS

Seven clinically suspected CIDP patients who did not fulfill EFNS/PNS electrodiagnostic criteria for demyelinating neuropathy were enrolled in our study. Routine nerve conduction studies, lumbar puncture, spinal cord magnetic resonance imaging and TST were detected. The patients were being treated with oral prednisone starting at 1 mg/kg daily. The overall disability sum score was performed to evaluate the effect of corticosteroids.

RESULTS

Twenty-eight motor nerves were tested with TST, two conduction blocks (CBs) were detected between the root emergence and the Erb point in six patients respectively and one CB was detected in one patient. Symptoms of all seven patients improved after treatment with oral prednisone.

CONCLUSION

TST can detect CBs located between the root emergence and the Erb point. TST is useful for early diagnosis of CIDP.

Potentiating paired corticospinal-motoneuronal plasticity after spinal cord injury

BACKGROUND

Paired corticospinal-motoneuronal stimulation (PCMS) increases corticospinal transmission in humans with chronic incomplete spinal cord injury (SCI).

OBJECTIVE/HYPOTHESIS

Here, we examine whether increases in the excitability of spinal motoneurons, by performing voluntary activity, could potentiate PCMS effects on corticospinal transmission.

METHODS

During PCMS, we used 100 pairs of stimuli where corticospinal volleys evoked by transcranial magnetic stimulation (TMS) over the hand representation of the primary motor cortex were timed to arrive at corticospinal-motoneuronal synapses of the first dorsal interosseous (FDI) muscle ∼1-2 ms before antidromic potentials were elicited in motoneurons by electrical stimulation of the ulnar nerve. PCMS was applied at rest (PCMS_rest) and during a small level of isometric index finger abduction (PCMS_active) on separate days. Motor evoked potentials (MEPs) elicited by TMS and electrical stimulation were measured in the FDI muscle before and after each protocol in humans with and without (controls) chronic cervical SCI.

RESULTS

We found in control participants that MEPs elicited by TMS and electrical stimulation increased to a similar extent after both PCMS protocols for ∼30 min. Whereas, in humans with SCI, MEPs elicited by TMS and electrical stimulation increased to a larger extent after PCMS_active compared with PCMS_rest. Importantly, SCI participants who did not respond to PCMS_rest responded after PCMS_active and those who responded to both protocols showed larger increments in corticospinal transmission after PCMS_active.

CONCLUSIONS

Our findings suggest that muscle contraction during PCMS potentiates corticospinal transmission. PCMS applied during voluntary activity may represent a strategy to boost spinal plasticity after SCI.

Detection of proximal conduction blocks using a triple stimulation technique improves the early diagnosis of Guillain-Barré syndrome

OBJECTIVE

Current diagnostic electrophysiological criteria can miss the early stages of Guillain-Barré syndrome (GBS). We evaluated the diagnostic efficiency of the triple stimulation technique (TST) in highlighting proximal conduction blocks (CBs) in patients who do not meet the electrophysiological criteria for GBS.

METHODS

All patients with a diagnosis of clinical GBS referred to our center between September 2014 and January 2016 were included in the study. For patients who did not fulfill the electrophysiological criteria of GBS, we performed the TST examination.

RESULTS

Among the 44 included patients, 86% fulfilled the electrophysiological criteria of GBS during the initial nerve conduction study (NCS). The six remaining patients had proximal CBs revealed by TST examination. Therefore, a combination of a conventional NCS and the TST allowed 100% of the patients to be electrophysiologically diagnosed.

CONCLUSIONS

TST is useful for the diagnosis of GBS in association with NCS, particularly in the early stages of the disease.

SIGNIFICANCE

TST is a useful tool for GBS diagnosis at the early stages of the disease.

Cauda Equina Conduction Time Determined by F-Waves in Normal Subjects and Patients With Neurogenic Intermittent Claudication Caused by Lumbar Spinal Stenosis

PURPOSE

Lumbar spinal stenosis typically presents with neurogenic intermittent claudication. The aim of this study was to investigate cauda equina conduction time (CECT) in patients with neurogenic intermittent claudication caused by lumbar spinal stenosis and its relationship with age and body height in normal subjects.

METHODS

The study included 172 normal subjects (group C) (mean age 44.1 ± 16.6 years; mean height 163.7 ± 8.9 cm). Forty-seven patients (group L) (mean age 71.3 ± 8.7 years; mean height 158.8 ± 11.2 cm) underwent surgery because of neurogenic intermittent claudication in cauda equina type of lumbar spinal stenosis. Motor-evoked potentials from the abductor hallucis were recorded. Magnetic stimulation was delivered at the S1 spinous process. Compound muscle action potentials (CMAPs) and F-waves were also recorded after supramaximal electric stimulation of tibial nerves. The peripheral motor conduction time (PMCT) was calculated from the latencies of CMAPs and F-waves as follows: (CMAPs + F-waves - 1)/2. The CECT was calculated by subtracting the onset latency of the motor-evoked potentials from PMCT.

RESULTS

The mean values for F-wave latencies, motor-evoked potential latencies, and CECT were 44.5 ± 3.3, 20.6 ± 1.8, and 3.4 ± 0.8 milliseconds, respectively. F-wave and motor-evoked potential latencies showed significant positive linear correlations with age and body height. However, no significant correlation was found between CECT and age (P = 0.43) or body height (P = 0.26). Mean CECT was 5.7 ± 1.5 in group L. There was a significant difference between groups C and L (P < 0.05).

CONCLUSIONS

The CECT value of normal subjects was 3.4 ± 0.8 milliseconds regardless of age and body height. We suggest that CECT may be a useful factor to consider when evaluating patients with neurogenic intermittent claudication.

Usefulness of cervical root magnetic stimulation in assessing proximal motor nerve conduction

OBJECTIVES

To evaluate the reliability and utility of cervical root magnetic stimulation in exploring proximal motor conduction.

METHODS

In 20 patients with demyelinating polyneuropathy (DPN), 20 patients with amyotrophic lateral sclerosis (ALS) and 25 healthy subjects, evoked compound muscle action potentials (CMAPs) were recorded from abductor digiti minimi muscle in response to electrical stimulation up to Erb's point and magnetic stimulation up to the cervical roots.

RESULTS

In all healthy and ALS subjects, magnetic root stimulation confirmed the absence of conduction abnormalities, including those in whom supramaximal responses at Erb's point were not achieved. In the DPN group, conduction block and/or temporal dispersion was revealed by magnetic root stimulation in 9 out of 20 patients (45%), 3 more than those detected at Erb's point.

CONCLUSIONS

Cervical root stimulation allowed clear distinction between motor neuronopathy and DPN. It is recommended as part of the routine evaluation of patients suspected of having DPN, especially when distal nerve studies are inconclusive.

Cauda equina conduction time in Guillain-Barré syndrome

The proximal segment of peripheral nerves is assumed to be involved in both demyelinating and axonal types of Guillain-Barré syndrome (GBS). However, electrophysiological examinations have not yet clarified if this segment is involved. We measured cauda equina conduction time (CECT) in nine demyelinating GBS and seven axonal GBS patients. Compound muscle action potentials (CMAPs) were recorded from the abductor hallucis muscle. Electrical stimulation was given at the ankle and the knee, and magnetic stimulation was given over the first sacral (S1) and first lumbar (L1) spinous processes using a magnetic augmented translumbosacral stimulation (MATS) coil. CECT was obtained by subtracting S1-level latency from L1-level latency. CECT was prolonged in all the patients with demyelinating GBS who had leg symptoms, whereas motor conduction velocity (MCV) at the peripheral nerve trunk was normal in all the patients. In all the patients with axonal GBS having leg symptoms, CECT and MCV were normal and no conduction blocks were detected between the ankle and the neuro-foramina. The cauda equina is much more frequently involved than the peripheral nerve trunk in demyelinating GBS. In axonal GBS, usually, CECT is normal and segmental lesions are absent between the ankle and the neuro-foramina. Therefore, the CECT measurement should be very useful for directly detecting demyelinating lesions in GBS.

Measurement of motor root conduction time at the early stage of Guillain-Barre syndrome

BACKGROUND AND PURPOSE

As they are mainly performed at distal nerve parts, routine electrophysiological examinations can fail to detect the abnormalities at the early stage of Guillain-Barre syndrome (GBS) because of predominant involvement of proximal nerve segments. Measurements focused on proximal conduction can provide additional findings. We investigated the diagnostic significance of motor root conduction time (MRCT) at the early stage of GBS.

METHODS

Study was performed in 30 healthy volunteers and within the first week of 12 patients with GBS. MRCT was calculated as the latency differences between motor nerve conduction time (MNCT) obtained by cervical magnetic stimulation and total peripheral motor conduction time obtained by electrical stimulation of ulnar nerve. Also MNCT/MRCT ratio was calculated in each subject.

RESULTS

  There were statistically significant differences between groups for MRCT (P < 0.0001) and MNCT/MRCT ratio (P < 0.0001). Although the F-wave latency at ulnar nerve was abnormal only in 33%, MRCT was significantly prolonged in 83% of patients. In three patients, prolongation of MRCT was the only abnormality at the first electrodiagnostic examination.

CONCLUSIONS

Motor root conduction time as a non-invasive method can provide additional and confirmative information at the early stage of GBS in which routine nerve conduction studies may fail to detect the focal demyelination.

Recommendations on diagnostic strategies for chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune mediated treatable peripheral neuropathy, the diagnosis of which is straightforward in more than half of cases. Numerous sets of electrophysiological criteria have been published. However, in some cases, electrophysiological data are not sufficient and patients that may benefit from treatment escape accurate diagnosis.

OBJECTIVE

To describe a step by step diagnostic procedure for neurologists facing a peripheral neuropathy of undetermined cause, to help make an accurate diagnosis of CIDP.

METHODS

A group of French experts was established, neurologists and neurophysiologists being recruited on the basis of personal experience with patients suffering from CIDP and also on publications in the field. A full literature review was conducted on the topic of diagnostic criteria and procedures for the diagnosis of CIDP, and meetings were scheduled to reach a consensus on the best diagnostic workup in different clinical situations.

RESULTS

Six meetings were conducted and a consensus was reached, based on the available literature and experience in the management of such patients. Discussions resulted in defining five clinical situations in which a diagnosis of CIDP may be considered, and procedures were detailed in each case, including the location of nerve biopsy and use of non-conventional electrophysiological testing and imaging procedures.

CONCLUSION

The guidelines in the diagnostic procedure reported here result from a consensus of French experts in the field of peripheral neuropathy and allow a diagnosis of CIDP to be made in the most frequently encountered situations. These recommendations may be of value for physicians as they rely on the rational use of available techniques in typical clinical situations.

Dynamic change of proximal conduction in demyelinating neuropathies: a cervical magnetic stimulation combined with maximum voluntary contraction

OBJECTIVE

To evaluate conduction abnormalities in the nerves innervating the proximal muscles in demyelinating neuropathies (DN) using cervical magnetic stimulation.

METHODS

We applied cervical root magnetic stimulation in the biceps brachii muscles and examined its activity-dependent conduction changes produced by maximal voluntary contraction (MVC) in 12 DN patients (seven chronic inflammatory demyelinating polyradiculoneuropathy and five multifocal motor neuropathy), six motor neuron disease (MND) patients, and 12 healthy volunteers.

RESULTS

Defining the upper normal limit of motor threshold (31%) and latency (6.7 ms) of the compound muscle action potential (CMAP) as mean+2SD, most DN patients revealed an abnormality in motor threshold (10/12) and latency (11/12) in contrast to MND patients (motor threshold (1/6) and latency (0/6)). These parameters contribute to the differentiation of DN from MND (P<0.01). Furthermore, the MVC maneuver transiently decreased the CMAP amplitude ratio (after MVC/before MVC x 100) in DN (83+/-18 %) compared with MND (P<0.01). Two of three DN patients who showed normal motor threshold or latency as in MND were successfully differentiated from MND by the MVC maneuver.

CONCLUSIONS

In DN patients, conduction abnormality in the nerves innervating the proximal muscles was revealed by cervical magnetic stimulation combined with the MVC maneuver.

SIGNIFICANCE

Our results suggested that conduction abnormalities in the proximal nerves innervating the proximal muscles could be evaluated by this method.

Proximal nerve conduction studies in chronic inflammatory demyelinating polyneuropathy

OBJECTIVE

The purpose of this study was to evaluate the sensitivity and specificity of proximal upper limb motor nerve conduction study abnormalities in chronic inflammatory demyelinating polyneuropathy (CIDP), using standard percutaneous stimulations up to Erb's point.

METHODS

Electrophysiologic data relating to proximal conductions of median and ulnar nerves of 22 patients with CIDP were retrospectively analyzed and compared to those of 22 controls with sensory neuropathy. Distal conduction results were also reviewed.

RESULTS

The findings demonstrate independent high sensitivity of abnormal upper limb proximal nerve conduction studies in CIDP. Demonstration of conduction block of >20% and temporal dispersion of >15% had low specificity. However, conduction block was highly specific with cut-off values of >30% at axilla and >50% at Erb's point. Specificity was considerably improved using a cut-off value of >30% at proximal levels for temporal dispersion. Diagnostic sensitivity improved significantly with proximal studies with the criteria used in this population. No adverse effects had occurred as result of proximal stimulations.

CONCLUSIONS

Proximal studies are safe, sensitive and reliable procedures in cases of suspected CIDP. Their use appears justified although adequate cut-off values are desirable to optimize their specificity.

SIGNIFICANCE

This study indicates that proximal upper limb nerve conductions are appropriate in investigating suspected CIDP, as detailed in recently established electrophysiologic criteria. However, specificity is largely dependent on cut-off values for conduction block and temporal dispersion.

Cervical nerve root stimulation. Part II: Findings in primary demyelinating neuropathies and motor neuron disease

OBJECTIVE

Cervical nerve root stimulation (CRS) allows the assessment of conduction in the proximal segments of motor fibers destined to the upper extremities, which are not evaluated by routine nerve conduction studies (NCS). Since many primary demyelinating polyneuropathies (PDP) are multifocal lesions may be confined to the proximal nerve segments. CRS may therefore increase the yield of neurophysiologic studies in diagnosing PDP.

METHODS

We reviewed clinical and neurophysiologic data from 38 PDP patients and compared them to 35 patients with motor neuron disease (MND), and 21 healthy controls (HC).

RESULTS

Mean onset-latency was significantly prolonged in PDP patients. The optimal onset-latency cutoff necessary to distinguish PDP from MND and controls was 17.5 ms for the abductor pollicis brevis (APB) and abductor digiti minimi (ADM), and 7 ms for Biceps and Triceps. Mean reduction in proximal to distal CMAP amplitude to APB and ADM was significantly greater in PDP patients, with an optimal cutoff in proximal to distal CMAP amplitude reduction necessary to distinguish PDP from MND and HC being 45%.

CONCLUSIONS

CRS is effective in distinguishing PDP from MND and HC based on prolonged onset latency and conduction block criteria.

SIGNIFICANCE

CRS may increase the diagnostic yield in cases where demyelinating lesions are confined to the proximal peripheral neuraxis.

A case of Lewis–Sumner syndrome with conduction abnormalities only in the brachial plexus and roots

We present a case of subacute weakness of one hand with unusual sensory involvement including the upper thorax. Despite normal distal conduction studies, a clinical diagnosis of Lewis-Sumner syndrome was made and the patient responded well to intravenous immunoglobulins. Repeated studies after clinical exacerbation finally proved the demyelinating nature of the neuropathy using proximal magnetic nerve stimulation. This case underlies the importance of seeking proximal conduction blocks in patients with suspected demyelinating neuropathy.

Polyradiculonévrites inflammatoires démyélinisantes chroniques : stratégie diagnostique

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) comprises a group of dysimmune neuropathies easily diagnosed in more than half of the patients. Diagnosis is based on clinical, electrophysiological and biological clues. In some patients, diagnosis is unclear because of the debated value of the available clues. In such circumstances, dysimmune neuropathies may not be diagnosed, leading to insufficient treatment. This is an important category of patients because immunomodulatory drugs have proven efficacy. The CIDP spectrum includes a relatively wide range of diseases. Besides the easily recognized classic forms, there are many clinical variants, sometimes with a paucisymptomatic presentation leading to uncertain diagnosis. The French CIDP study group has established guidelines for diagnostic strategy in CIDP patients. The first part of this paper is devoted to the clinical aspects of the disease, classical forms and variants. In the second part, the results of electrophysiological studies are reported. In a third chapter, complementary examinations useful for diagnosis are discussed. The fourth chapter deals with the diagnostic strategy, discussed in relation to the different situations which may be encountered in clinical practice. details the technical modalities of appropriate electrophysiological studies and presents normal results together with those indicating demyelinating neuropathy. Nerve biopsy technique and results are given in appendix II.

Optimizing the use of electrophysiology in the diagnosis of chronic inflammatory demyelinating polyneuropathy: a study of 20 cases

Current electrophysiologic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP) are highly specific but poorly sensitive. The required extensiveness and best practical way of performing nerve conduction studies to achieve optimal sensitivity remain unknown. We here initially retrospectively analyzed the motor nerve conduction study results of 20 consecutive patients with a clinical diagnosis of CIDP (four performed prior to, and 16 after, treatment initiation) to assess the sensitivity of six published sets of criteria (Nicolas et al., 2002; Thaisetthawatkul et al., 2002; Ad Hoc Subcommittee of the American Academy of Neurology AIDS Taskforce, 1991; Magda et al., 2003; Hughes et al., 2001; Saperstein et al., 2001), as well as four combinations (Nicolas et al., 2002; Ad Hoc Subcommittee of the American Academy of Neurology AIDS Taskforce, 1991; Hughes et al., 2001; Saperstein et al., 2001, each individually combined with Thaisetthawatkul et al., 2002). Sensitivity was highest for the combination of Nicolas et al. (2002) and Thaisetthawatkul et al. (2002) (100%). We then determined the sensitivity of this combined criteria, using five different, hypothetical, nerve conduction study protocols, applied retrospectively to the neurophysiologic data of our 20 patients (exclusive upper limb studies with proximal stimulations; exclusive lower limb studies; full forearm and foreleg studies without proximal stimulations; right-sided studies with proximal stimulations; and left-sided studies with proximal stimulations). The findings showed that exhaustive upper limb or, alternatively, four-limb forearm and foreleg testing would have proved considerably more sensitive than unilateral or lower limb studies to achieve an electrophysiologic diagnosis of CIDP.

Motoneuron excitability and the F wave

For three motoneuron pools that differ in excitability to Ia inputs [tibialis anterior (TA), abductor pollicis brevis (APB), and soleus], F-wave parameters were measured at rest, during voluntary contraction, and following prolonged vibration. There was an inverse relationship between F-wave chronodispersion and F-wave persistence at rest, and this appeared to be related to the ease of recording the H reflex for the motoneuron pool. During a steady voluntary contraction, overall F-wave activity increased in amplitude but decreased in duration for TA and APB. Following vibration of the test muscle at 50 HZ for 10 min there was a long-lasting depression of the H reflexes of TA and APB, but no significant change in F-wave measurements. These findings are consistent with the view that reflex discharges can prevent F waves in low-threshold motor units, and that chronodispersion is affected by the extent of reflex activity; that is, chronodispersion and related F-wave measurements do not measure motor properties exclusively. The findings also suggest that F waves provide a flawed measure of the excitability of the motoneuron pool.

Nerve conduction studies in selected peripheral nerve disorders

PURPOSE OF REVIEW

The physiological properties of nerve and muscle are influenced by pathological changes and the aim of this review is to discuss recent contributions of electrophysiological studies to the understanding and diagnosis of selected peripheral nerve disorders. The relationships between pathology and physiology emphasize the close interdependence between electrophysiological studies, clinical deficits and other laboratory information. Attention should be paid to the strengths and limitations of electrophysiological methods, considering their impact on diagnosis and treatment of patients.

RECENT FINDINGS

Several studies have shown particular pathophysiological profiles associated with different antibody subtypes in autoimmune peripheral neuropathies and this association further supports the suggestion of pathological specificity in both acute and chronic neuropathy. The sensitivity and specificity of physiological profiles therefore become increasingly important since some of these neuropathies are accessible to treatment. On the other hand, the pathophysiological and clinical profiles may be heterogeneous in patients with some disorders. This could be related to a more indistinct division between different types of pathology with increased understanding of pathogenetic mechanisms. Moreover, new insights into disturbed axonal function have stimulated attempts to develop methods to explore normal and diseased human nerve function.

SUMMARY

The exploration of axonal membrane and ion-channel function has become accessible using studies of excitability and are of potential value where conventional studies only provide nonspecific evidence of the number of fibers and the integrity of myelin. These studies will presumably become increasingly important in the years ahead considering the lack of understanding of the functional disturbances in axonal neuropathies.