Inclusion body myositis mimicking motor neuron disease.

OBJECTIVE: To describe the clinical and electrophysiologic features of patients with inclusion body myositis that was misinterpreted as motor neuron disease. PATIENTS AND METHODS: We retrospectively retrieved the medical records of 70 patients with a pathologic diagnosis of inclusion body myositis. From this group, we selected those who had been first diagnosed as having motor neuron disease or amyotrophic lateral sclerosis. We reviewed the clinical, electrophysiologic, laboratory, and morphologic studies. RESULTS: Nine (13%) of 70 patients with inclusion body myositis had been diagnosed as having motor neuron disease. Six of the 9 patients had asymmetric weakness; in 4 the distal arm muscles were affected. Eight patients had finger flexor weakness. Tendon reflexes were preserved in weak limbs in 6, hyperactive in 2, and absent in 1. Four patients had dysphagia. Fasciculation was seen in 2 patients. None had definite upper motor neuron signs or muscle cramps. Routine electromyographic studies showed fibrillation potentials and positive sharp waves in all 9. Fasciculation potentials were seen in 7 and long-duration polyphasic motor unit potentials were seen in 8. There was no evidence of a myogenic disorder in these 9 patients. Muscle biopsy was done because of slow progression or prominent weakness of the finger flexors and was diagnostic of inclusion body myositis. A quantitative electromyogram was myopathic in 4 of the 5 patients studied. CONCLUSIONS: Inclusion body myositis may mimic motor neuron disease. Muscle biopsy and quantitative electromyographic analysis are indicated in patients with atypical motor neuron disease, especially those with slow progression or early and disproportionate weakness of the finger flexors.

Electrophysiologic studies in critical illness associated weakness: myopathy or neuropathy--a reappraisal.

OBJECTIVE: Unexplained weakness in critically ill patients is recognized with increasing frequency. However, it is debated whether the condition is a peripheral neuropathy or a myopathy. Diagnostic difficulties can arise from multiple sources that are not generally a factor in other neuromuscular conditions. Conventional electrodiagnostic techniques may provide only non-specific data, clinical examination is often hampered, and muscle biopsy is not a practical screening tool. METHOD: To improve diagnostic yield, we studied 22 consecutive patients with critical illness associated weakness with additional electrodiagnostic techniques, including direct muscle stimulation, quantitative electromyography, and motor unit number estimation. RESULTS: The applied techniques supported an underlying myopathy in all the patients examined. The diagnosis was confirmed by muscle biopsy in 9 patients. Additional lesser features of neuropathy were concomitantly present in one patient who also underwent sural nerve biopsy. CONCLUSIONS: The study suggests that myopathy is much more common than polyneuropathy in critical illness. Suspicion of this entity should be high in this setting even without exposure to corticosteroids or non-depolarizing blocking agents.

Diagnostic value of electrophysiological tests in patients with sciatica.

OBJECTIVES: To assess the diagnostic value of electrophysiological tests in patients with sciatica. MATERIALS AND METHODS: The diagnostic value of electrophysiological tests were evaluated in 25 patients with monoradicular sciatica. The electrophysiological study included dermatomal somatosensory evoked potentials, electromyography, F-wave latencies, H-reflexes and motor and sensory nerve conduction determinations. The results of the electrophysiological examinations were evaluated blindly, and the test results were analysed separately by a receiver operating characteristic (ROC) analysis. Furthermore, the 5 modalities were evaluated jointly and analysed by a decision-analytic regret function. RESULTS: A high predictive value was found for the H-reflex examination, but low for the other modalities. When the 5 modalities were evaluated jointly, a non-significant decrease in expected regret from the pre-test situation of 0.96 to a value of 0.93 in post-test situation was revealed. CONCLUSION: Electrophysiological testing is not sufficient as stand-alone examination in patients with sciatica.

EMG evidence of myopathy and the occurrence of titin autoantibodies in patients with myasthenia gravis.

We studied 65 patients with myasthenia gravis (MG). Clinical, neurophysiological, immunological, and histological findings suggested the coexistence of a presumed autoimmune myopathy. The clinical features were persistent pyridostigmine-resistant weakness and atrophy of striated muscles. The myopathy was found more often in patients with late-onset MG than in those with early-onset (37% vs 13%). Patients with myopathy were also prone to have other immune disorders (47% vs 13%). Elevated titres of antibodies against titin were detected more often in patients with electromyography (EMG) evidence of myopathy than in the sera of those without, and only in late-onset MG cases.

Acute and chronic neuropathies: new aspects of Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy, an overview and an update.

During the last 15 years new information about clinical, electrophysiological, immunological and histopathological features of acute and chronic inflammatory neuropathies have emerged. Thus, the Guillain-Barré syndrome (GBS) is no longer considered a simple entity. Subtypes of the disorder besides the typical predominant motor manifestation, are recognized, i.e. a cranial nerve variant with ophthalmoplegia, ataxia and areflexia, an immune-mediated primary motor axonal neuropathy (AMAN), and a motor-sensory syndrome (AMSAN). Also, the clinical pattern of GBS is related to preceding viral or bacterial infections. Two types of acute motor paralysis have been described, one with slow and incomplete recovery, another with recovery times identical with acute inflammatory demyelinating polyneuropathy (AIDP). Histologically, the first is characterized by Wallerian degeneration of motor roots and peripheral motor nerve fibres. In the latter anti-GM antibodies bind to the nodes of Ranvier producing a failure of impulse transmission. Motor-point biopsies have shown denervated neuromuscular junctions and a reduced number of intramuscular nerve fibres. Molecular mimicry has been postulated as a possible mechanism triggering GBS. Thus, in the cranial variant antibodies to ganglioside GQ1b recognizes similar epitopes on Campylobacter jejuni strains and similar observations apply to anti-GM1 antibodies. Chronic inflammatory demyelinating polyneuropathy (CIDP) also has several different clinical presentations such as a pure motor syndrome, a sensory ataxic variant, a mononeuritis multiplex pattern, relapsing GBS, and a paraparetic subtype. Each of the acute and the subtypes have different, more or less distinct, electrophysiologic and pathological findings. Instructive patient stories are presented together with there electrophysiologic and biopsy findings.

Lymphoproliferative disorders and motor neuron disease: an update.

We studied 26 patients with both motor neuron disease and lymphoproliferative disease (LPD). Twenty-three patients had definite or probable upper motor neuron signs; none had electrophysiologic evidence of motor neuropathy. LPD syndromes comprised Waldenström's macroglobulinemia, multiple myeloma, chronic lymphocytic leukemia, follicular cell lymphoma, and Hodgkin's disease. In all but one patient, the cause of disability or death was neurologic. LPD was confined to bone marrow in 14 patients; eight of 14 had monoclonal paraproteinemia. One patient had LPD discovered at autopsy. Treatment of LPD in 20 patients resulted in neurologic improvement in 1 patient and arrest in another; both had progressive spinal muscular atrophy. Eleven patients were worse and 13 died. At least 30 cases have been reported from other centers, bringing the total to 56. Among the unusual reported concomitants were POEMS (polyneuropathy, organomegaly, endocrinopathy, myeloma, and skin changes) syndrome of myeloma and angiotropic lymphoma.

The role of quantitative electromyography in inclusion body myositis.

OBJECTIVE AND METHODS: Inclusion body myositis is said to have both myopathic and neurogenic features on electrophysiological tests. Twenty one studies from 20 patients with biopsy defined inclusion body myosis, 13 of whom had quantitative electromyography (qEMG), were reviewed to determine if this technique added diagnostic specificity (one patient had both needle EMG and a later study with qEMG before muscle biopsy). RESULTS: Excessive numbers of polyphasic motor unit potentials (MUPs) (> 12% per muscle) were seen in 11 of the 13 patients. In 10 of 13 patients, mean MUP duration was abnormally reduced (26% to 48%). In three patients, mean MUP duration was abnormally reduced only after polyphasic MUPs were excluded. In all 13 patients, the simple MUP duration was reduced. Myopathy was unequivocally diagnosed in all 13 studies that included qEMG; of the remaining eight patients, the conclusions of the electrophysiological studies without qEMG was myopathy (one), neurogenic (four) or non-diagnostic (three). CONCLUSIONS: There is no evidence of a neurogenic component in inclusion body myosis if qEMG is used. Quantitative EMG is often necessary to make an electrophysiological diagnosis of a myogenic disorder in patients with inclusion body myosis.

Motor neuron disease, lymphoproliferative disease, and bone marrow biopsy.

Some have suggested that nonfamilial motor neuron disease (MND) may be autoimmune, and the neurological disorder may benefit from immunotherapy. There have been reports of over 30 cases of lymphoproliferative disease (lymphoma, multiple myeloma, Waldenström's macroglobulinemia) with MND, and these patients might he offered immunosuppressive therapy. Bone marrow examination might increase the sensitivity of the diagnostic workup for lymphoma and other lymphoproliferative disorders. We examined the bone marrow in our first evaluation of 161 patients with MND seen at Columbia-Presbyterian Medical Center during 1991-1994. Four of 161 patients (2.5%) had lymphoproliferative disease in the marrow; only 1 of these had a monoclonal paraprotein. Routine bone marrow examination of patients with MND increases the diagnostic yield of lymphoproliferative diseases. The frequency of these bone marrow abnormalities in comparison with a group of age-matched control subjects should be studied further.

Diabetic peripheral neuropathy: a clinicopathologic and immunohistochemical analysis of sural nerve biopsies.

We performed quantitative immunohistochemical studies of sural nerve biopsy specimens from 20 patients to determine whether endoneurial and epineurial lymphocytic infiltration occurs in diabetic nerves. The diabetic nerves contained a mean of 129 CD3+ cells per tissue section compared to 19 cells in patients with chronic neuropathy matched for the histologic severity of disease, and 0-5 cells in normal control nerves. The T-cell infiltrates in the diabetic nerves were predominantly of the CD8+ cell type. Activated endoneurial lymphocytes expressed immunoreactive cytokines and major histocompatibility class II antigens. Microvasculitis was found in 12 (60%) patients. Infiltrative T cells may contribute to the pathogenesis of diabetic neuropathy through a variety of effector mechanisms.

Anti-MAG and anti-SGPG antibodies in neuropathy.

We compared the binding of human antibodies from patients with neuropathy to the myelin-associated glycoprotein (MAG), to its cross-reactive glycolipid sulfoglucuronyl paragloboside (SGPG), and to sections of peripheral nerve. Titers were correlated with the clinical presentation and results of electrophysiological and pathological studies. Most patients had a predominantly sensory or sensorimotor demyelinating neuropathy and highly elevated antibodies to both MAG and SGPG, but 2 had highly elevated antibodies to MAG alone, and 1 to SGPG alone. Two patients had predominantly motor neuropathy and highly elevated antibodies to SGPG which reacted with MAG by Western blot but not by enzyme-linked immunosorbent assay. One patient had amyotrophic lateral sclerosis and antibodies to SGPG but not to MAG. These studies indicate that the neuropathic syndrome associated with anti-MAG or -SGPG antibodies are more heterogeneous than previously suspected, and that although most of the antibodies react with both MAG and SGPG, some may react with MAG or SGPG alone.

Sensory pathophysiology in chronic acquired demyelinating neuropathy.

Pathophysiological changes in sensory fibres in chronic acquired demyelinating neuropathy (CADP) are poorly understood, and it is not known to what extent sensory loss may be due to axonal loss or to conduction block. Motor and sensory nerve condition were studied in 18 patients with CADP to delineate abnormalities in the compound sensory action potential (CSAP) recorded proximally along the limb. To distinguish small CSAPs from noise, near-nerve needle electrodes and electronic averaging were used. In all, 58 motor and 78 sensory nerves in the upper and lower limbs were studied, and in 29 nerves, motor and sensory conduction was compared over the same proximal and distal segments of the upper limbs. The proximal/distal amplitude ratio (P/D ratio) of the compound muscle action potential (CMAP) was reduced in 76% of the nerves compared with only 21% of the CSAPs. The amplitudes of CMAPs evoked and of CSAPs recorded distally were reduced to the same extent. The prolongation of the distal motor latency (DML) was linearly related to the reduction in amplitude of the CMAP whereas reduction of the distal sensory conduction velocity (SCVd) mainly occurred if the amplitude of the CSAP was reduced more than 70%. The proximal motor nerve conduction velocity (MCVp) was reduced by 40-50%, twice as much as the reduction in distal MCV (MCVd) (calculated from the reciprocal DML), and related to the reduction in the P/D ratio of the CMAP. The proximal SCV (SCVp) decreased approximately 20%, similar to the reduction in SCVd and out of proportion to the marked reduction of the MCVp. The results suggest different pathophysiological changes in sensory and motor fibres in CADP. Thus, nerve fibre loss could account for most of the abnormal parameters in sensory conduction, whereas demyelination was the dominating cause of motor nerve dysfunction.

[X-linked recessive bulbospinal neuropathy (Kennedy syndrome)]. / X-bunden recessiv bulbospinal neuronopati (Kennedys syndrom).

A case of X-linked recessive bulbospinal neuronopathy is reported. Neurophysiological findings were consistent with chronic partial denervation (motor axonopathy) and large fibre sensory axonopathy. DNA analysis showed an abnormal increased size of tandem CAG repeats.

Motor conduction parameters in neuropathies associated with anti-MAG antibodies and other types of demyelinating and axonal neuropathies.

We measured residual latency (RL), motor conduction velocity (MCV), and terminal latency index (TLI) in 15 patients with neuropathy and anti-MAG or SGPG antibodies and compared these to values obtained in 103 patients with other types of polyneuropathy (PN) and to 57 normal subjects. Ten patients had anti-MAG antibody titers of 25,600 or higher, and 5 had titers between 800 and 12,600. Patients with the highest titers had longer RL, slower MCV and shorter TLI than those with lower titers, acute or chronic inflammatory demyelinating PN, hereditary neuropathy, and metabolic or axonal neuropathy. In contrast F-wave latencies did not contribute to the differentiation between the groups of demyelinating neuropathies. RL and TLI correlated best with anti-MAG antibody titers, whereas there was a poor correlation with anti-SGPG titers suggesting that MAG more than SGPG may be the antigen in PN, and that the distal nerves are affected more than their proximal segments. The RL rather than TLI turned out to be the best variable to classify the demyelinating type of anti-MAG neuropathy. Sural nerve biopsy in 5 of the patients with the highest titer of anti-MAG antibodies showed deposits of IgM and C3 on the myelin sheaths, pronounced demyelination and widening of the myelin lamellae. In 4 of the patients with lower titers demyelination was absent or less pronounced.