Selective paraspinal muscle amyotrophy.

A 56-year-old female presented with mild low back pain. Examination revealed severe, selective atrophy of the thoracic and lumbar paraspinal muscles. Fibrillations were seen in the paraspinal muscles on EMG. Limb EMG was normal. Biopsy of the gluteus maximus was normal. Paraspinal muscle biopsy revealed neurogenic features. Atrophy of the thoracic and lumbar paraspinal muscles was noted on magnetic resonance imaging. This patient has selective amyotrophy of the thoracic and lumbar paraspinal muscles. This may be an addition to the spectrum of 'benign focal amyotrophy'. The differential diagnosis of paraspinal muscle weakness is discussed.