Background. Posterior interosseous nerve (PIN) palsy may present with various symptoms, and may resemble cervical spondylosis.
Case report. We report about a 59-year-old patient with cervical spondylosis which delayed the diagnosis of posterior interosseous nerve (PIN) palsy due to an intermuscular lipoma. Initial right hand paraesthesias
and clumsiness, together with MR findings of right C5-C6 and C6-C7 foraminal stenosis, misled the diagnostic investigation. The progressive loss of extension of all right hand fingers brought to detect a painless mass compressing the PIN. Electrophysiological studies confirmed a right radial motor neuropathy at the level of the forearm.
Results. Surgical tumor removal and nerve decompression resulted in a gradual motor deficits recovery.
Conclusions. A thorough clinical examination is paramount, and electrophysiology may differentiate between cervical and peripheral nerve lesions. Ultrasonography and MR offer an effective evaluation of lipomas, which represent a rare cause of PIN palsy. Surgical decompression and lipoma removal generally determine excellent prognoses, with very few recurrences.