We evaluated the central (motor cortex to C8 motoneuron) and peripheral (C8 motoneuron to the muscle) motor conduction in 14 limbs of 7 patients with the intermediate form of spinal muscular atrophy (SMA II). The central motor conduction time (CMCT) was calculated using motor evoked potentials (MEPs) by transcranial magnetic stimulation and the results of a conventional F wave study. Peripheral conduction abnormality was found in 6 median nerves (43%) and 10 ulnar nerves (71%). Even in these patients with peripheral conduction abnormalities, the CMCT was consistently normal whenever the MEP was recorded. These results indicate that the motor conduction of the corticospinal fibers remains normal in SMA II.

Adolescent↗

PubMedDate not supplied

Skeletal muscle involvement in mucopolysaccharidosis type IIA: severe type of Hunter syndrome.

A patient with mucopolysaccharidosis type IIA (MPS IIA) and progressive gait disturbance is described. The histopathology of biopsied muscle was studied; Dorling's method revealed muscle fibers and interstitial cells containing metachromatic granules which suggested the storage of sulfated acidic glycosaminoglycans. Electron microscopy demonstrated that the membrane-bound vacuoles were present in muscle fibers, subsarcolemmal area, vascular endothelial cells, satellite cells, and endomysial fibroblasts. Besides clinical features, this ultrastructural pathology in MPS IIA muscles of MPS IIA was more severe than MPS IIB muscles. The accumulation of glycosaminoglycans in muscle tissue may be an additional factor contributing to gradual motor impairment of patients with MPS IIA.

Biopsy↗

PubMedDate not supplied

Glycogen storage disease with normal acid maltase: skeletal and cardiac muscles.

We report a 5-year-old boy with lysosomal glycogen storage disease and normal acid maltase activity. This patient, the fourth reported in the literature, was referred to our hospital for evaluation of elevated serum GOT, GPT, and CK activities. He had neither muscle weakness nor atrophy. Echocardiography demonstrated marked thickening of the intraventricular septum and left ventricular wall which indicated hypertrophic cardiomyopathy. Biopsied skeletal muscle disclosed massive accumulation of glycogen and autophagic vacuoles. Electron microscopy of biopsied cardiac muscle revealed severe myofibrillar disruption with marked accumulation of free and intralysosomal glycogen. Activities of all major glycolytic enzymes in skeletal muscle, including acid maltase, were normal. It is unknown why muscle lysosomes appeared to be unable to digest the trapped glycogen despite the presence of acid maltase. Our findings illustrate the importance of performing skeletal muscle investigation during childhood in patients with hypertrophic cardiomyopathy.

Biopsy↗

PubMedDate not supplied

Rett syndrome: findings suggesting axonopathy and mitochondrial abnormalities.

We report the histopathologic findings of 3 sural nerve biopsies and 1 muscle biopsy from 3 patients with Rett syndrome. The 3 sural nerve biopsies demonstrated a few ultrastructural abnormalities, including the presence of many Pi-granules and mitochondrial changes in the cytoplasm of Schwann cells, occasional bands of Büngner and onion-bulb formations, and mitochondrial alterations in myelinated axons. Morphometric analysis disclosed reduction in the number of large myelinated fibers with normal densities in comparison to those of an age-matched normal control. Light microscopic examination of the biopsied muscle from a 6-year-old patient with Rett syndrome revealed the existence of many small, dark, angulated fibers with NADH-TR staining. Ultrastructural investigation of the muscle confirmed the presence of the dumbbell-shaped mitochondria. Peripheral nerve involvement and the possibility of mitochondrial abnormalities in Rett syndrome were suggested by the results.

Axons↗

PubMedDate not supplied

Proximal and distal motor nerve conduction velocities in Werdnig-Hoffmann disease.

Using the latencies of M and F responses, we assessed motor nerve conduction velocity along the entire course of the median and ulnar nerves from the spinal cord to the muscle in 14 patients with the less severe forms of Werdnig-Hoffmann disease. In these forms, the motor nerve conduction velocities were decreased significantly over both proximal (cord-to-elbow) and distal (elbow-to-wrist) segments in both the nerves as compared with normal values; however, the mean motor nerve conduction velocities in the proximal segments were faster than those in the distal segments by about the same amount as the normal controls. These findings indicate that motor conduction abnormalities in Werdnig-Hoffmann disease are diffuse over the entire course of the nerve and appear to eliminate a dying-back process in which the affected axons are severely damaged, beginning with the more distal sites.

Adolescent↗