Selective calf weakness suggests intraspinal pathology, not peripheral neuropathy
P. R. Bourque and P. J. Dyck
Peripheral Neuropathy Research Laboratory, Mayo Clinic, Rochester, Minn.
Four patients, referred as having peripheral neuropathy, were noted to be
able to walk on their heels but not on their toes. In each, intraspinal
disease was found: ependymoma of the filum terminale, spinal muscular
atrophy, spinal stenosis, and meningeal carcinomatosis. By comparison, in
86 cases of hereditary motor and sensory neuropathy type 1, ankle plantar
flexors were never weaker than ankle dorsiflexors. Patients with greater
weakness in plantar flexors than in dorsiflexors should be suspected of
having intraspinal disease rather than peripheral neuropathy. Physiologic
and biomechanical factors may explain why muscles innervated by the
peroneal nerve are weaker, or graded weaker, in peripheral neuropathy.
