[Differential diagnosis in early muscular hypotonia: spinal atrophy]

Changes in type, size and structure of muscle fibres were analyzed in 68 biopsies with clinical and morphological signs of spinal atrophy. Reliability of clinical prebioptic diagnosis was evaluated in comparison with bioptic finding and final diagnosis. Muscle biopsy is often to be performed in spite of apparently unambiguous clinical and electromyographical finding. Contribution of biopsy to the diagnosis of spinal atrophy with characteristical grouping of atrophic fibres is undisputable in most cases. However, unproper sampling in excessively atrophic areas and structural "myogenic" changes can made the bioptic diagnosis difficult or impossible. Size analysis of muscle fibres proved participation of both the basic fibre types in atrophy with increase in number of immature type 2c fibres, and prevalence of type 1 fibres in hypertrophic areas (compensatory hypertrophy or re-innervation respectively) where also hybrid fibres can often be found during transformation of their type. Angular atrophic fibres occurring in hypertrophic fibre groups gave evidence of continuous or secondary denervation in benign forms of spinal atrophy. The author found regressive structural changes in benign form and in malignant Werdnig-Hoffman atrophy either--though less extensive.