Asymmetric Muscle Weakness Research Articles

Somatic mosaicism of a point mutation in the dystrophin gene in a patient presenting with an asymmetrical muscle weakness and contractures

We describe a patient with somatic mosaicism of a point mutation in the dystrophin gene causing benign muscular dystrophy with an unusual asymmetrical distribution of muscle weakness and contractures. To our knowledge this is the first patient with asymmetrical weakness and contractures in an ambulatory patient with a dystrophinopathy.

Abstracts of the 8th Meeting of the Italian Peripheral Nerve Study Group: 82

A 69‐year‐old right‐handed man was recently referred to our institution with a two‐month history of diplopia and ptosis in his left eye: the ocular symptoms typically fluctuates during the day, being least severe in the morning and worsening as the day progress or while reading or driving. Neostigmine injection produced a clear improvement of weakness. The serum concentration of anti‐AChR antibody was elevated > 8.4 nmol/L (NV < 0.4); a chest CT scan was unremarkable with no evidence of mediastinal mass. The clinical picture and laboratory tests support the diagnosis of ocular myasthenia. His past medical history was insignificant until the age of 59. At that time, he complained with a diffuse, slightly asymmetrical muscle weakness both in the upper and lower limbs and sensory symptoms of glove and stocking distribution (numbness). A progressive course over months was seen with hand and anterior leg muscles hypertrophy becoming evident. Strength was decreased distally greater than proximally in the upper and lower extremities. Deep tendon reflexes were absent. The cerebrospinal fluid demonstrated a protein level of 72 mg/dl (NV < 45 mg/dl). Nerve conduction study showed a multifocal sensory‐motor polyneuropathy with both conduction block/temporal dispersion of the C‐MAP and slowing of the velocity. A diagnosis of chronic inflammatory polyneuropathy (CIDP) was considered and the patient was treated with steroids, plasmapheresis and azathiaprine: after a slight improvement, the condition has been stabilized. Both MG and CIDP have been individually associated with disorders of presumed autoimmune pathogenesis. Their concurrence is rarely found (less than 10 cases to the best of our knowledge): although the existence of this syndrome can be strongly supported by the clinical, electrophysiological and laboratory data, a common basic abnormality of immune regulation is still unknown.

A biomechanical model on muscle forces in the transfer of spinal load to the pelvis and legs

Based on musculoskeletal anatomy of the lower back, abdominal wall, pelvis and upper legs, a biomechanical model has been developed on forces in the load transfer through the pelvis. The aim of this model is to obtain a tool for analyzing the relations between forces in muscles, ligaments and joints in the transfer of gravitational and external load from the upper body via the sacroiliac joints to the legs in normal situations and pathology. The study of the relation between muscle coordination patterns and forces in pelvic structures, in particular the sacroiliac joints, is relevant for a better understanding of the aetiology of low back pain and pelvic pain. The model comprises 94 muscle parts, 6 ligaments and 6 joints. It enables the calculation of forces in pelvic structures in various postures. The calculations are based on a linear/non-linear optimization scheme. To gain a better understanding of the function of individual muscles and ligaments, deviant properties of these structures can be preset. The model is validated by comparing calculations with EMG data from the literature. For agonistic muscles, good agreement is found between model calculations and EMG data. Antagonistic muscle activity is underestimated by the model. Imposed activity of modelled antagonistic muscles has a minor effect on the mutual proportions of agonistic muscle activities. Simulation of asymmetric muscle weakness shows higher activity of especially abdominal muscles.

Scoliosis caused by section of dorsal spinal nerve roots.

Experimental evidence has accumulated in recent years to suggest that scoliosis can be caused by asymmetrical spinal muscle weakness due to sensorineural loss, though this suggestion has not achieved universal acceptance. The evidence is supported by histopathological observations on cases of clinical idiopathic scoliosis. A study is presented in which cynomolgus monkeys had one, two or three dorsal spinal nerve roots cut. Scoliosis developed, convex to the damaged side; its severity was dependent on the number of nerve roots cut. Section of the first lumbar dorsal spinal nerve root had a marked tendency to cause scoliosis. The study supports the view that scoliosis may be caused by asymmetrical paraspinal muscle weakness acting through loss of proprioception.