Amyloid polyneuropathy caused by wild-type transthyretin.

INTRODUCTION: Amyloidosis derived from transthyretin (TTR) molecules is typically caused by mutations of the TTR gene. METHODS: We describe an elderly patient with a severe length-dependent polyneuropathy that unexpectedly proved to be caused by wild-type transthyretin amyloidosis. RESULTS: The diagnosis was made by muscle biopsy, because no amyloid deposits were found in the biopsied nerve segment. Most cases of wild-type transthyretin amyloidosis occur in elderly patients with cardiomyopathy, but a few cases of polyneuropathy have been reported. CONCLUSIONS: This entity is especially noteworthy in light of emerging treatment options for hereditary transthyretin amyloidosis, which are likely to also be beneficial in wild-type disease.

Focal amyotrophy in multiple sclerosis.

INTRODUCTION: The assumption that multiple sclerosis (MS) is purely a white matter disease has been challenged in recent years by observations of axonal damage and neuronal loss in gray matter of the cortex, subcortex, and spinal cord. METHODS: We report the case of a 71-year-old man with primary progressive MS and longstanding right arm weakness who presented with intermittent right arm pain. RESULTS: Neurological examination showed atrophy, weakness, and hyporeflexia, and electromyography (EMG) showed acute and chronic partial denervation in multiple segments of the right arm. Magnetic resonance imaging (MRI) demonstrated asymmetric volume loss and increased T2 signal in the right anterior spinal cord from C3 to C7, with no evidence of nerve root compression. CONCLUSIONS: Lower motor neuron involvement of his right arm was caused by MS with involvement of either the anterior horn cells or the intraspinal motor nerve roots.

Sarcoid polyneuropathy masquerading as chronic inflammatory demyelinating polyneuropathy.

INTRODUCTION: Sarcoid polyneuropathy is a rare and clinically heterogeneous disorder that may be the initial presentation of sarcoidosis. METHODS: We report the clinical, electrophysiological, and pathological findings of a patient who carried a diagnosis of sensory-predominant chronic inflammatory demyelinating polyneuropathy (CIDP) for over a decade but was ultimately found to have sarcoid polyneuropathy. RESULTS: A 36-year-old man presented with a several-week history of gait difficulty and muscle cramps. He had a diagnosis of CIDP but had not received lasting benefit from steroid-sparing immunosuppressive drugs. Electrodiagnostic studies were consistent with a chronic demyelinating polyradiculoneuropathy with conduction blocks. After he developed systemic symptoms, tissue biopsies revealed granulomatous disease. Symptoms improved with steroid therapy. CONCLUSIONS: Sarcoid polyneuropathy presents a diagnostic challenge, but, in patients with atypical neuropathy, characteristic systemic symptoms, or a poor response to standard treatment, nerve and muscle biopsies can help diagnose this treatable disorder.

Muscle-specific kinase antibodies: a novel cause of peripheral nerve hyperexcitability?

INTRODUCTION: Antibodies that target the postsynaptic neuromuscular junction (NMJ) protein, muscle-specific kinase (MuSK), have been associated with myasthenia gravis (MG), often with cramps and fasciculations, after administration of acetylcholinesterase inhibitors (AChE-I). METHODS: In this report, 2 patients are described with elevated MuSK antibodies and evidence of peripheral nerve hyperexcitability (PNH) unrelated to AChE-I medication. RESULTS: Patient 1 presented with facial neuromyotonia and fasciculations, without overt weakness. EMG studies demonstrated myokymic discharges in facial muscles, with bursts of discharges after voluntary activation, and widespread fasciculation potentials in limb muscles. Patient 2 presented with bulbar weakness and fasciculations in the tongue and limbs, initially diagnosed as bulbar-onset amyotrophic lateral sclerosis. Subsequent investigation identified the presence of MuSK antibodies. CONCLUSIONS: We hypothesize that MuSK antibodies may induce these phenotypes through disruptive actions at the NMJ, in particular the binding of acetylcholinesterase (AChE) to MuSK via its collagen Q (ColQ) tail, producing a reduction in synaptic AChE activity.

Magnetic resonance neurography in extraspinal sciatica.

BACKGROUND: Sciatica without evidence of lumbosacral root compression is often attributed to piriformis syndrome. However, specific diagnostic tools have not been available to demonstrate sciatic nerve entrapment by the piriformis muscle. OBJECTIVE: To evaluate the use of magnetic resonance (MR) neurography in identifying abnormalities of the sciatic nerve in patients with unexplained sciatica. DESIGN: Case series from a retrospective medical record review. PATIENTS: Fourteen patients with sciatic distribution pain and normal results on MR imaging for lumbosacral radiculopathy were referred for MR neurography of the lumbosacral plexus and sciatic nerves. RESULTS: In 12 patients, MR neurography demonstrated increased fluid-attenuated inversion recovery signal in the ipsilateral sciatic nerve. In most patients, this abnormal signal was seen at the sciatic notch, at or just inferior to the level of the piriformis muscle. To date, 4 patients have undergone surgical decompression, with excellent relief of symptoms in 3 of them. CONCLUSION: Magnetic resonance neurography often identifies an abnormal increased signal in the proximal sciatic nerve in patients with extraspinal sciatica and allows more accurate diagnosis of sciatic nerve entrapment in suspected cases.

Cervical Myelopathy Caused by Injections into the Neck.

Three cases of longitudinally extensive cervical myelopathies temporally associated with neck injections are presented. The spinal cord injury was similar radiographically, despite a number of different needle approaches and substances injected. In recent years, there have been reports of an acute cervical myelopathy immediately following an injection procedure in the neck. Various explanations have been offered for this unfortunate complication, including (1) direct injection into the cord leading to traumatic injury, (2) injection of particulate matter into the arterial supply of the cord causing microvascular embolism and spinal cord infarction, and (3) intraneural injection of the chemical with centripetal spread of the injectant from the nerve trunk to the substance of the cord. The merits of each of these 3 mechanisms in explaining these cases are discussed. Albeit rare, acute cervical myelopathy should be considered a potential complication from any deep injection of chemicals into the neck.

Dermatomyositis with inclusion body myositis pathology.

The pathogenic role of inflammation in inclusion body myositis (IBM) remains uncertain. A 63-year-old man developed a severe, rapidly progressive myopathy with clinical features typical of dermatomyositis (DM), but muscle pathology was typical of IBM. Treatment with prednisone and methotrexate resulted in complete remission of symptoms. Together with two similar cases reported previously, this case suggests that the inflammatory process of DM may trigger the pathologic changes of IBM.

Adult nemaline myopathy with trabecular muscle fibers.

The term "trabecular myopathy" has been used to designate a syndrome resembling limb-girdle muscular dystrophy in which the predominant pathological feature is an abundance of lobulated or trabecular muscle fibers. However, the validity of this nosological entity has not been verified. Herein we describe a 63-year-old man with a severe, progressive myopathy who exhibited the typical pathological features of both trabecular myopathy and nemaline myopathy in association with a biclonal gammopathy. In this case, adult-onset nemaline myopathy was probably the primary disease process. The diagnostic significance of trabecular muscle fibers remains uncertain.

Myasthenia gravis and Lambert-Eaton myasthenic syndrome in the same patient.

An 18-year-old-woman developed symptoms of generalized myasthenia gravis (MG). Antibodies to the acetylcholine receptor were found in her serum, but electrodiagnostic testing showed abnormalities typical of the Lambert-Eaton myasthenic syndrome (LEMS). Following thymectomy, the thymus gland showed thymic hyperplasia typical of MG, and the patient responded to treatment with 3,4-diaminopyridine and pyridostigmine. There have been few reports in the literature of MG and LEMS coexisting in the same patient. In this case, electrodiagnostic tests, antibody studies, thymus pathology, and response to treatment suggest that both disorders contributed to the patient's symptoms. Thymic hyperplasia, so far only known to be associated with MG, provides strong evidence that both diseases were symptomatic.

Muscle cramps.

Muscle cramps are a common problem characterized by a sudden, painful, involuntary contraction of muscle. These true cramps, which originate from peripheral nerves, may be distinguished from other muscle pain or spasm. Medical history, physical examination, and a limited laboratory screen help to determine the various causes of muscle cramps. Despite the "benign" nature of cramps, many patients find the symptom very uncomfortable. Treatment options are guided both by experience and by a limited number of therapeutic trials. Quinine sulfate is an effective medication, but the side-effect profile is worrisome, and other membrane-stabilizing drugs are probably just as effective. Patients will benefit from further studies to better define the pathophysiology of muscle cramps and to find more effective medications with fewer side-effects.