Sciatic schwannoma of the thigh causing foot pain mimicking plantar neuropathy

Two patients with plantar foot pain, one mistakenly thought to have tarsal tunnel syndrome, had complete resolution of pain after resection of a sciatic nerve schwannoma of the midthigh. The entire extent of the sciatic nerve should be evaluated in patients presenting with unilateral, neuropathic foot pain. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:528–530, 1998.     

Cervical magnetic stimulation

We stimulated the cervical region with a 9-cm-diameter magnetic coil on centered on the spinous processes in 21 normal subjects. We obtained maximal amplitudes with clockwise coil current in right-sided upper extremity muscles and counterclockwise coil current in left-sided upper extremity muscles. Optimal stimulation sites for biceps, triceps, and abductor digiti minimi were C-3 or C-4, C-4 or C-5, and C-4, C-5, or C-6, respectively. The latencies of the muscle responses varied little in the same subject in spite of marked amplitude changes due to suboptimal position of the coil or submaximal stimulator output. In abductor digiti minimi, the amplitude of the muscle response on cervical magnetic stimulation was 9 to 100% of the supramaximal amplitude on wrist electrical stimulation. We established normal values for latency, amplitude, and interside differences for the above 3 upper extremity muscles. The findings were reproducible, and the latencies obtained with large coils from different manufacturers in the same subjects were comparable. We found no advantage in bipolar recording over tendon-belly montage. Comparison of magnetic and electrical needle root stimulation in the same subjects showed that the magnetic stimulus was more proximal in biceps and triceps, and that the site of excitation was approximately the same in abductor digiti minimi. Indirect assessment of the longitudinal site of excitation based on F-wave minimal latency indicated that excitation occurred within millimeters of the emergence of axon of the peripheral motor neuron.     

Magnetic stimulation F-responses

We used the 9 cm Cadwell magnetic coil, stimulating at the wrist, to obtain simultaneous median and ulnar nerve F-responses. Surface recording was performed from conventional thenar and hypothenar sites. It is known that with this type of coil it is difficult to accomplish selective supramaximal stimulation of the median or ulnar nerve individually. We found it possible, however, to record a compound muscle action potential of supramaximal or near supramaximal amplitude, as well as F-responses, in both thenar and hypothenar muscles simultaneously. We assessed this technique for F-response latency determination in controls and patients with carpal tunnel syndrome. In controls, there was no significant difference in the F-minimal latency or the F-minimum-maximum range obtained by the two methods. In patients with carpal tunnel syndrome, with median F-responses very delayed or absent on conventional testing, magnetically elicited thenar F-responses were of shorter latency, similar to F's recorded in the hypothenar muscles, suggesting they were recorded from ulnar innervated thenar muscles. Although magnetic stimulation allows simultaneous determination of median and ulnar F-latencies, sparing patients several painful stimuli, and shortening the electrophysiologic examination, magnetic stimulation in patients with carpal tunnel syndrome may elicit thenar recorded F-responses that are not of median origin. Use of this technique is limited by the lack of focality of the stimulus, which has been the major limiting factor in its use on peripheral nerves.     

Novel and recurrent mutations in lamin A/C in patients with Emery‐Dreifuss muscular dystrophy

Emery‐Dreifuss muscular dystrophy (EDMD) is characterized by slowly progressive muscle wasting and weakness; early contractures of the elbows, Achilles tendons, and spine; and cardiomyopathy associated with cardiac conduction defects. Clinically indistinguishable X‐linked and autosomal forms of EDMD have been described. Mutations in the STA gene, encoding the nuclear envelope protein emerin, are responsible for X‐linked EDMD, while mutations in the LMNA gene encoding lamins A and C by alternative splicing have been found in patients with autosomal dominant, autosomal recessive, and sporadic forms of EDMD. We report mutations in LMNA found in four familial and seven sporadic cases of EDMD, including seven novel mutations. Nine missense mutations and two small in‐frame deletions were detected distributed throughout the gene. Most mutations (7/11) were detected within the LMNA exons encoding the central rod domain common to both lamins A/C. All of these missense mutations alter residues in the lamin A/C proteins conserved throughout evolution, implying an essential structural and/or functional role of these residues. One severely affected patient possesed two mutations, one specific to lamin A that may modify the phenotype of this patient. Mutations in LMNA were frequently identified among patients with sporadic and familial forms of EDMD. Further studies are needed to identify the factors modifying disease phenotype among patients harboring mutations within lamin A/C and to determine the effect of various mutations on lamin A/C structure and function. © 2001 Wiley‐Liss, Inc.     

Bilateral aortoostial coronary artery disease: moyamoya of the heart?

Moyamoya is a vascular occlusive disease typically limited to the cerebral arterial system. We report a case of severe stenosis of the left main and right coronary arteries occurring in association with moyamoya disease, supporting the concept that moyamoya may be an intracranial manifestation of a systemic arterial disorder.     

Comparison of electric and magnetic coil stimulation in the supraclavicular region.

We compared the compound motor action potentials (CMAPs) evoked in the biceps, triceps, and abductor digiti minimi (ADM) muscles by conventional electrical stimulation at Erb's point (EP), and by magnetic coil stimulation of the supraclavicular region in 11 normal subjects. We found that magnetic coil stimulation was less effective than conventional stimulation in activating motor fibers in the brachial plexus in 45% of the recordings analyzed. CMAP amplitudes greater than those obtained with EP electrical stimulation were seen in 16% of recordings with supraclavicular magnetic stimulation, and in 33% of recordings with cervical magnetic stimulation, indicating that EP electrical stimulation is submaximal in a large proportion of cases.     

Herpes simplex labialis and trigeminal neuropathy

Three patients had a transient trigeminal sensory disturbance associated with an ipsilateral herpes simplex (HS) labialis lesion. These cases support the theory that isolated trigeminal sensory disturbance may be caused by intermittent reactivation of HS virus in the trigeminal ganglion.     

Novel and recurrent mutations in lamin A/C in patients with Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is characterized by slowly progressive muscle wasting and weakness; early contractures of the elbows, Achilles tendons, and spine; and cardiomyopathy associated with cardiac conduction defects. Clinically indistinguishable X-linked and autosomal forms of EDMD have been described. Mutations in the STA gene, encoding the nuclear envelope protein emerin, are responsible for X-linked EDMD, while mutations in the LMNA gene encoding lamins A and C by alternative splicing have been found in patients with autosomal dominant, autosomal recessive, and sporadic forms of EDMD. We report mutations in LMNA found in four familial and seven sporadic cases of EDMD, including seven novel mutations. Nine missense mutations and two small in-frame deletions were detected distributed throughout the gene. Most mutations (7/11) were detected within the LMNA exons encoding the central rod domain common to both lamins A/C. All of these missense mutations alter residues in the lamin A/C proteins conserved throughout evolution, implying an essential structural and/or functional role of these residues. One severely affected patient possesed two mutations, one specific to lamin A that may modify the phenotype of this patient. Mutations in LMNA were frequently identified among patients with sporadic and familial forms of EDMD. Further studies are needed to identify the factors modifying disease phenotype among patients harboring mutations within lamin A/C and to determine the effect of various mutations on lamin A/C structure and function.     

The world epidemic of sleep disorders is linked to vitamin D deficiency

An observation of sleep improvement with vitamin D supplementation led to a 2 year uncontrolled trial of vitamin D supplementation in 1500 patients with neurologic complaints who also had evidence of abnormal sleep. Most patients had improvement in neurologic symptoms and sleep but only through maintaining a narrow range of 25(OH) vitamin D3 blood levels of 60-80 ng/ml. Comparisons of brain regions associated with sleep-wake regulation and vitamin D target neurons in the diencephalon and several brainstem nuclei suggest direct central effects of vitamin D on sleep. We propose the hypothesis that sleep disorders have become epidemic because of widespread vitamin D deficiency. The therapeutic effects together with the anatomic-functional correspondence warrant further investigation and consideration of vitamin D in the etiology and therapy of sleep disorders.