Triple-stimulation technique in multifocal neuropathy with conduction block

Novel approaches to assessing upper motor neuron dysfunction in motor neuron disease/amyotrophic lateral sclerosis: IFCN handbook chapter

Identifying upper motor neuron (UMN) dysfunction is fundamental to the diagnosis and understanding of disease pathogenesis in motor neuron disease (MND). The clinical assessment of UMN dysfunction may be difficult, particularly in the setting of severe muscle weakness. From a physiological perspective, transcranial magnetic stimulation (TMS) techniques provide objective biomarkers of UMN dysfunction in MND and may also be useful to interrogate cortical and network function. Single, paired- and triple pulse TMS techniques have yielded novel diagnostic and prognostic biomarkers in MND, and have provided important pathogenic insights, particularly pertaining to site of disease onset. Cortical hyperexcitability, as heralded by reduced short interval intracortical inhibition (SICI) and increased short interval intracortical facilitation, has been associated with the onset of lower motor neuron degeneration, along with patterns of disease spread, development of specific clinical features such as the split hand phenomenon, and may provide an indication about the rate of disease progression. Additionally, reduction of SICI has emerged as a potential diagnostic aid in MND. The triple stimulation technique (TST) was shown to enhance the diagnostic utility of conventional TMS measures in detecting UMN dysfunction in MND. Separately, sophisticated brain imaging techniques have uncovered novel biomarkers of neurodegeneration that have bene associated with progression. The present review will discuss the utility of TMS and brain neuroimaging derived biomarkers of UMN dysfunction in MND, focusing on recently developed TMS techniques and advanced neuroimaging modalities that interrogate structural and functional integrity of the corticomotoneuronal system, with an emphasis on pathogenic, diagnostic, and prognostic utility.

Clinical diagnostic utility of transcranial magnetic stimulation in neurological disorders. Updated report of an IFCN committee

The review provides a comprehensive update (previous report: Chen R, Cros D, Curra A, Di Lazzaro V, Lefaucheur JP, Magistris MR, et al. The clinical diagnostic utility of transcranial magnetic stimulation: report of an IFCN committee. Clin Neurophysiol 2008;119(3):504-32) on clinical diagnostic utility of transcranial magnetic stimulation (TMS) in neurological diseases. Most TMS measures rely on stimulation of motor cortex and recording of motor evoked potentials. Paired-pulse TMS techniques, incorporating conventional amplitude-based and threshold tracking, have established clinical utility in neurodegenerative, movement, episodic (epilepsy, migraines), chronic pain and functional diseases. Cortical hyperexcitability has emerged as a diagnostic aid in amyotrophic lateral sclerosis. Single-pulse TMS measures are of utility in stroke, and myelopathy even in the absence of radiological changes. Short-latency afferent inhibition, related to central cholinergic transmission, is reduced in Alzheimer's disease. The triple stimulation technique (TST) may enhance diagnostic utility of conventional TMS measures to detect upper motor neuron involvement. The recording of motor evoked potentials can be used to perform functional mapping of the motor cortex or in preoperative assessment of eloquent brain regions before surgical resection of brain tumors. TMS exhibits utility in assessing lumbosacral/cervical nerve root function, especially in demyelinating neuropathies, and may be of utility in localizing the site of facial nerve palsies. TMS measures also have high sensitivity in detecting subclinical corticospinal lesions in multiple sclerosis. Abnormalities in central motor conduction time or TST correlate with motor impairment and disability in MS. Cerebellar stimulation may detect lesions in the cerebellum or cerebello-dentato-thalamo-motor cortical pathways. Combining TMS with electroencephalography, provides a novel method to measure parameters altered in neurological disorders, including cortical excitability, effective connectivity, and response complexity.

Evidence base for investigative and therapeutic modalities in chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy

Chronic inflammatory demyelinating polyneuropathy, its variants and multifocal motor neuropathy belong to a spectrum of peripheral nerve disorders with complex dysimmune disease mechanisms. Awareness of the unique clinical phenotypes but also heterogeneity between patients is vital to arrive at early suspicion and ordering appropriate tests. This includes requirements for optimal electrodiagnostic protocol, aimed to capture sufficient electrophysiologic evidence for relevant abnormalities, a case-based approach on the eventual need to further expand the diagnostic armamentarium and correct reading of their results. Considerable phenotypical variation, diverse combinations of abnormalities found on diagnostic tests and heterogeneity in disease course and treatment response, all contribute to widespread differences in success rates on timely diagnosis and optimal treatment. We aim to provide a practical overview and guidance on relevant diagnostic and management strategies, including pitfalls and present a summary of the relevant novel developments in this field.

Assessing the upper motor neuron in amyotrophic lateral sclerosis using the triple stimulation technique: A multicenter prospective study

OBJECTIVE

To evaluate the relevance of transcranial magnetic stimulation (TMS) using triple stimulation technique (TST) to assess corticospinal function in amyotrophic lateral sclerosis (ALS) in a large-scale multicenter study.

METHODS

Six ALS centers performed TST and conventional TMS in upper limbs in 98 ALS patients during their first visit to the center. Clinical evaluation of patients included the revised ALS Functional Rating Scale (ALSFRS-R) and upper motor neuron (UMN) score.

RESULTS

TST amplitude ratio was decreased in 62% of patients whereas conventional TMS amplitude ratio was decreased in 25% of patients and central motor conduction time was increased in 16% of patients. TST amplitude ratio was correlated with ALSFRS-R and UMN score. TST amplitude ratio results were not different between the centers.

CONCLUSIONS

TST is a TMS technique applicable in daily clinical practice in ALS centers for the detection of UMN dysfunction, more sensitive than conventional TMS and related to the clinical condition of the patients.

SIGNIFICANCE

This multicenter study shows that TST can be a routine clinical tool to evaluate UMN dysfunction at the diagnostic assessment of ALS patients.

Comparison of MRI and motor evoked potential with triple stimulation technique for the detection of brachial plexus abnormalities in multifocal motor neuropathy

BACKGROUND

Conduction blocks (CB) are the diagnostic hallmark of multifocal motor neuropathy (MMN). Conventional nerve conduction studies cannot detect CB above Erb's point. Our purpose was to compare the performance of the motor evoked potential with triple stimulation technique (MEP-TST) and MRI in the detection of abnormalities of the brachial plexus.

METHODS

Examinations were performed on 26 patients with MMN (11 definite, 6 probable, 9 possible), of whom 7 had no CB.

RESULTS

MEP-TST detected proximal CB in 19/26 patients. Plexus MRI showed T2 hyperintensity in 18/26 patients, with nerve enlargement in 14/18. A combination of both techniques increased the detection rate of brachial plexus abnormalities to 96% of patients (25/26).

CONCLUSIONS

MEP-TST and MRI have high sensitivities for detecting brachial plexus abnormalities. A combination of the two techniques increases the detection rate of supportive criteria for the diagnosis of MMN.

Triple Stimulation Technique in Amyotrophic Lateral Sclerosis

PURPOSE

To identify upper motor neuron (UMN) dysfunction using the triple stimulation technique (TST) in amyotrophic lateral sclerosis (ALS).

METHODS

Fifty ALS and 42 non-ALS patients were examined clinically, using conventional transcranial magnetic stimulation and TST.

RESULTS

For ALS patients presenting with UMN in tested limb, the TST amplitude ratio was abnormal in 25 of 28 patients (89.3%). For ALS patients without UMN signs, 6 of 22 patients (27.3%) had an abnormal TST ratio. When clinical signs were not present, both abnormal resting motor threshold and TST indicated a UMN involvement. In non-ALS patients with central motor conduction disorders, the percentage of patients with an abnormal TST was higher for those presenting with clinical UMN signs (9/12, 75.0%) than for those without these signs (1/8, 12.5%).

CONCLUSIONS

Triple stimulation technique appears to be an accurate, early measure for detecting clinical and subclinical UMN abnormalities in ALS. Triple stimulation technique could also be useful to investigate central motor conduction abnormalities in other disorders.

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.

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.

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.

Proximal conduction block in the pharyngeal-cervical-brachial variant of Guillain-Barré syndrome

INTRODUCTION

Conduction block (CB) has been included in the Rajabally criteria for axonal Guillain-Barré syndrome (GBS). Because the nerve roots may be affected early in GBS, detection of proximal CB by the triple stimulation technique (TST) can be useful.

METHODS

We describe TST findings in 2 patients who presented with the pharyngeal-cervical-brachial (PCB) variant of axonal GBS.

RESULTS

In the first patient, although conventional nerve conduction studies (NCS) did not fit electrodiagnostic criteria for axonal GBS, the TST detected proximal CB in the median and ulnar nerves. In the second patient, NCS fulfilled criteria for axonal GBS, and the TST detected proximal CB in the median nerve. After plasmapheresis, NCS and TST findings were normalized, suggesting reversible conduction failure rather than demyelinating CB.

CONCLUSION

The TST may be useful for diagnosis of PCB when NCS remain inconclusive. The technique provides additional clues for classifying PCB into the acute nodo-paranodopathies.

The pathogenesis of multifocal motor neuropathy and an update on current management options

Multifocal motor neuropathy (MMN) is a rare and disabling disease. Several experimental studies and clinical data are strongly suggestive of an immune-mediated pathogenesis, although underlying mechanisms in MMN seem to be very specific, mainly because of the presence of IgM anti-GM1 serum antibodies and the dramatic response to intravenous immunoglobulins (IVIg). The origin of antiganglioside antibodies and the way in which they act at the molecular level remain unclear. Several studies have demonstrated the key role of complement activation in the underlying mechanisms of MMN, as well as in animal models of acute motor axonal neuropathy (AMAN). Deposition of the membrane attack complex may disrupt the architecture of the nodes of Ranvier and paranodal areas, causing local disruption of nodal sodium-channel clusters. In patients with MMN, muscle weakness is the consequence of conduction blocks (CB), which leads to secondary axonal degeneration, consequently the aim of the treatment is to reverse CB at early stages of the disease. High-dose immunoglobulin is to date the only therapy which has proven efficacy in MMN patients in providing transient improvement of muscle strength, but long-term follow-up studies show a progressive motor decline. Therefore, other therapies are needed to improve the conduction nerve properties in long-term design. The reduction of complement activation and more generally the gain in paranodal stabilization could be directions for future therapeutic strategies.

Normative data and long-term test-retest reliability of the triple stimulation technique (TST) in multiple sclerosis

OBJECTIVES

Transcranial magnetic stimulation is useful for the assessment of cortico-spinal tract integrity in multiple sclerosis (MS). An advanced approach is the triple stimulation technique (TST), utilizing a combination of central and peripheral stimuli, reducing individual response variability. Although TST measures have been implemented in longitudinal studies, basic methodological data on temporal properties of abnormal TST values in MS are sparse.

METHODS

Normative TST data were obtained from 48 healthy participants. Longitudinal measures were derived from 17 MS-patients (relapsing-remitting: N=10; clinically isolated syndrome: N=7) prior to, three and twelve months following therapy initiation. Intraclass correlations were used to examine test-retest reliability. Complementary, patient ambulation and cognition were assessed.

RESULTS

Patient TST parameters were abnormal, involving excellent test-retest reliability and stable mean values. Cognitive and motor performance improved.

CONCLUSIONS

Results are the first to show that abnormal TST values in MS, reflecting diagnostic utility, are highly reliable in a long-term follow-up. Methodological properties are adequate for a longitudinal implementation of TST. Parameters were insensitive to alterations in cognitive/motor functioning. Sensitivity may be verified in subgroups with different treatment regimes.

SIGNIFICANCE

Results provide new normative data, support diagnostic utility of TST measures in MS, and confirm their long-term robustness.

Multifocal motor neuropathy

PURPOSE OF REVIEW

Multifocal motor neuropathy (MMN) remains a difficult issue for neurologists, as its clinical and electrophysiological presentation may be atypical, and because no alternative treatment to periodic immunoglobulin infusions has been assessed in its long-term management. This review intends to summarize the most recent advances in the diagnosis and treatment of MMN.

RECENT FINDINGS

Recent reports have focused on atypical onset and unusual clinical presentation. Several sophisticated electrophysiological techniques, as triple stimulation, may help establish the presence of conduction blocks, as well as MRI findings. A recent immunological study focused on the detection of serum IgM binding to NS6S heparin disaccharide. In another research article, it was proposed that the use of combinatorial glycoarray or ELISA may increase the diagnostic sensitivity of antiglycolipid antibody testing. Subcutaneous immunoglobulin may represent an interesting alternative option to intravenous immunoglobulin. Lastly, recently reported open-label clinical trials with complement inhibitors and anti-CD20 monoclonal antibody may constitute a first step for further developments.

SUMMARY

Diagnostic criteria for MMN are well established, but challenging situations still occur. Progresses in neurophysiologic and other laboratory tests may help in clarifying doubtful diagnoses. Current research into the pathophysiology of MMN is required to determine the future treatment targets.

Multifocal motor neuropathy: current therapies and novel strategies

Multifocal motor neuropathy (MMN) is a purely motor mononeuritis multiplex characterized by the presence of conduction block on motor but not on sensory nerves and by the presence of high titers of anti-GM1 antibodies. Several data point to a pathogenetic role of the immune system in this neuropathy, although this has not yet been proved. Several uncontrolled studies and randomized controlled trials have demonstrated the efficacy of therapy with high-dose intravenous immunoglobulin (IVIg) in MMN. However, this therapy has a short-lasting effect that needs to be maintained with periodic infusions. This can be partly overcome by the use of subcutaneous immunoglobulin (SCIg) at the same dose. The high cost and need for repeated infusions have led to the search for other immune therapies, the efficacy of which have not yet been confirmed in randomized trials. In addition, some therapies, including corticosteroids and plasma exchange, are not only ineffective but have been associated with clinical worsening. More recently, a number of novel therapies have been investigated in MMN, including interferon-β1a, the anti-CD20 monoclonal antibody rituximab and the complement inhibitor eculizumab. Preliminary data from open-label uncontrolled studies show that some patients improve after these therapies; however, randomized controlled trials are needed to confirm efficacy. Until then, IVIg (and SCIg) remains the mainstay of treatment in MMN, and the use of other immune therapies should only be considered for patients not responding to, or becoming resistant to, IVIg.

Electrophysiological measurement at Erb's point during the early stage of Guillain-Barré syndrome

This study aimed to find the electrophysiological significance of proximal nerve stimulation at Erb's point during the early stage of Guillain-Barré syndrome (GBS). Twenty-one healthy volunteers and 13 patients within the first week of GBS were studied. Latency and amplitude at wrist, elbow and Erb's point, and F waves were calculated after compound muscle action potentials (CMAP) were obtained at the median and ulnar nerve. There were statistically significant differences between groups for CMAP latency and amplitude at Erb's point for the median (p=0.005 and 0.001, respectively) and ulnar nerves (p=0.007 and 0.007, respectively). Latency or amplitude of CMAP after Erb's point stimulation was abnormal in 77% of patients while F wave latency was abnormal in only 46% of patients. Conduction block was observed in 62% of patients. Abnormal parameters at Erb's point were the only abnormality in four patients at the first electrophysiological examination. We conclude that electrophysiological examination at Erb's point is a simple and non-invasive method that can be used in the early stage of GBS, especially for patients who exhibit normal F waves and nerve conduction studies at distal nerves.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a chronic immune-mediated neuropathy that is particular for its asymmetric, multifocal, purely motor clinical presentation, often related to the distribution of individual nerves. Upper limbs are usually primarily and more severely affected, but lower limbs may be involved during the course of the disease. The hallmark of the disease is the presence, in electrophysiological studies, of persistent conduction blocks in the affected motor nerves, located outside the usual sites of nerve compression, contrasting with normal sensory nerve conduction velocities. The most typical laboratory finding is the presence of high levels of serum IgM antibodies to the ganglioside GM1, and less frequently to asialo-GM1, GD1a or GM2. These striking features may help distinguishing this neuropathy from both motor neuron disease and other chronic immune-mediated neuropathies. Several randomized controlled trials (RCT) have established the efficacy of high-dose intravenous immunoglobulin (IVIg), as well as subcutaneous immunoglobulin (SCIg). However, this therapy has a short-lasting effect, and need to be maintained with periodic infusions. This disappointing status has led to the search of other immune therapies whose efficacy has not been so far confirmed in RCT. This review intends to summarize current contents in the diagnosis and the treatment of MMN.

[Focal neuropathy]

The differential diagnosis of focal neuropathy continues to be one of the main tasks in peripheral neurology and clinical neurophysiology. In this respect a detailed medical history a topologically oriented clinical examination based on profound anatomical knowledge and a targeted neurophysiological examination are the cornerstones of successful diagnosis. Refined imaging techniques, such as sonography and magnetic resonance imaging provide - additional and valuable morphological information especially in atypical or unresolved cases. The aim of this overview is therefore to summarize the spectrum of focal neuropathy and diagnostic approaches, particularly in terms of a well-founded differential diagnosis.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) was first described in 1988 as a purely motor neuropathy affecting multiple motor nerves. The diagnosis was based entirely on demonstrating electrophysiological evidence of a conduction block (CB) that selectively affected motor axons, with sparing of sensory axons even through the site of motor CB. Subsequently, a similar disorder was reported but with absence of demonstrable CB on routine nerve conduction studies and there is still some debate as to whether MMN without CB is related to MMN. MMN is thought to be an inflammatory neuropathy related to an immune attack on motor nerves. The conventional hypothesis is that the primary pathology is segmental demyelination, but recent research raises the possibility of a primary axonopathy. Anti-GM1 antibodies can be found in some patients but it is unclear whether these antibodies are pathogenic. Intravenous immunoglobulin is the mainstay of treatment but other immunosuppressive treatments can also be effective.

Predicting a positive response to intravenous immunoglobulin in isolated lower motor neuron syndromes

OBJECTIVE

To determine clinically related characteristics in patients with pure lower motor neuron (LMN) syndromes, not fulfilling accepted diagnostic criteria, who were likely to respond to intravenous immunoglobulin (IVIg) treatment.

METHODS

Demographic, clinical, laboratory and neurophysiological characteristics were prospectively collected from patients with undifferentiated isolated LMN syndromes who were then treated with IVIg. Patients were classified as either responders or non-responders to therapy with IVIg based on clinical data and the two groups were compared.

RESULTS

From a total cohort of 42 patients (30 males, 12 females, aged 18-83 years), 31 patients responded to IVIg and 11 did not. Compared to patients that developed progressive neurological decline, responders were typically younger (45.8 compared to 56.0 years, P<0.05) and had upper limb (83.9% compared to 63.6%, NS), unilateral (80.6% compared to 45.5%, P<0.05), and isolated distal (54.1% compared to 9.1%, P<0.05) weakness. Patients with predominantly upper limb, asymmetrical, and distal weakness were more likely to respond to IVIg therapy. Of the patients who responded to treatment, only 12.9% had detectable GM(1) antibodies and conduction block (not fulfilling diagnostic criteria) was only identified in 22.6%.

CONCLUSIONS

More than 70% of patients with pure LMN syndromes from the present series responded to treatment with IVIg therapy, despite a low prevalence of detectable GM(1) antibodies and conduction block. Patients with isolated LMN presentations, not fulfilling accepted diagnostic criteria, may respond to IVIg therapy, irrespective of the presence of conduction block or GM(1) antibodies, and should be given an empirical trial of IVIg to determine treatment responsiveness.

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.

Prospective, blind study of the triple stimulation technique in the diagnosis of ALS

OBJECTIVE

To evaluate the diagnostic yield of magnetic cortical stimulation with the triple stimulation technique (TST) to identify upper motor neuron (UMN) involvement in patients suspected of having ALS.

METHODS

Fifty-nine patients were recruited to undergo TST in addition to the standard work-up for suspected motor neuron disease. TST combines transcranial magnetic stimulation of the motor cortex with collision studies, which results in a higher sensitivity in detecting UMN involvement. Primary outcome was the number of abnormal TST results in patients with possible ALS. The positivity rate was converted to the number needed to test with TST (NN-TST) for one extra diagnosis of ALS.

RESULTS

Fifty patients underwent TST. In the total group (n=59), 18 patients had a motor neuron disorder but did not fulfil criteria for 'probable' or 'definite' ALS. In four of these patients TST was abnormal (NN-TST, 4.5). One TST was erroneously interpreted as abnormal. TST findings were normal in inclusion body myositis and peripheral nerve disorders.

CONCLUSION

This prospective and blind study confirms open studies of TST in the evaluation of ALS. We suggest that TST can be used to arrive at a diagnosis of 'probable' or 'definite' ALS in patients lacking UMN signs in the upper extremities.