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Calf Enlargement in S1 Radiculopathy

Kessler, Stacy M. MD; Litchy, William J. MD

American Journal of Physical Medicine & Rehabilitation: March 2014 - Volume 93 - Issue 3 - p 275–276
doi: 10.1097/PHM.0b013e31827d6907
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From the Department of Physical Medicine and Rehabilitation (SMK) and Department of Neurology (WJL), Mayo Clinic, Rochester, Minnesota.

All correspondence and requests for reprints should be addressed to: William J. Litchy, MD, Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.

Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.

A 47-yr-old man presented to the neurology clinic with chronic right leg weakness and calf asymmetry. He had an 8-yr history of right leg pain that was worse with sitting and better with standing and a 30-mo history of right leg weakness. His pain resolved after a right L5–S1 hemilaminectomy. Nine months before presentation, his right calf was noted to be larger than the left. Ultrasound was negative for deep venous thrombosis. The remainder of his medical history was unremarkable.

Physical examination revealed a right calf circumference of 45 cm compared with 39 cm on the left (Fig. 1). Right peroneus longus weakness was noted, along with loss of right Achilles reflex. The remainder of the neurologic examination was normal.



His workup included magnetic resonance imaging of the lumbar spine, magnetic resonance imaging of the right lower limb, and nerve conduction study/electromyography. Magnetic resonance imaging of the lumbar spine showed granulation tissue and disc extrusion at L5/S1 with contact of the traversing right S1 nerve root (Fig. 2). Right lower limb magnetic resonance imaging noted normal common peroneal and tibial nerves with increased T2 signal of the soleus, flexor hallucis, and medial gastrocnemius.



The results of the nerve conduction studies were normal. The EMG revealed large motor unit potentials in predominantly S1 innervated muscles, including medial and lateral gastrocnemius, gluteus maximus, and S1 paraspinals. There were dense complex repetitive discharges in the right medial and lateral gastrocnemius muscle. The electrophysiologic findings correlated with an old right S1 radiculopathy with secondary hypertrophy of the gastrocnemius muscle.

Whereas denervation is typically associated with muscle tissue wasting, ipsilateral calf enlargement is an uncommon but well-recognized phenomenon associated with S1 radiculopathy.1 The pathophysiology is unclear, but theories include muscle fiber hypertrophy of nondenervated muscle fibers, abnormal stretching of muscle fibers, and abnormal electrical activity.1–4 EMG and lumbar spine imaging are helpful to confirm diagnosis of a radiculopathy. Surgical decompression has not been shown to result in resolution of hypertrophy.1

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