Quiz Form

Question Date: 28/09/2023

Question: Which of these features is not a hallmark of a neurogenic process in muscle biopsy?

Options:

• Angulated fibers
• Type 2 fiber atrophy
• Group atrophy
• Fiber type grouping

Correct Answer: Type 2 fiber atrophy

Explaination: Denervation in muscle leads to various changes. When the muscle fiber loses its nerve supply, it becomes atrophic and gets squeezed between other normal fibers producing angulated fibers. Following denervation, adjacent muscle fibers may get reinnervated and when that nerve degenerates, adjacent fibers degenerate, producing group atrophy. With repeated denervation and reinnervation, large groups of contiguous fibers are supplied by the same nerve. Since all fibers supplied by same nerve are of the same fiber type, groups if type 1 fibers next to groups of type 2 fibers replace the normal mosaic pattern (Fiber type grouping). Type 2 fiber atrophy is common and nonspecific, resulting from disuse, steroid use and many other causes.

Reference: Doughty C T, Amato AA. Disorders of Skeletal Muscle. Bradley and Daroffs Neurology in Clinical Practice. 2022. Ch 1091978