Reversible neuropathy after chemotherapy for metastatic adenocarcinoma from an unknown primary tumor to the sural nerve.

Adenocarcinomas and other various tumors are known to metastasize to various locations without any significant predilection and the metastasis could be the first presentation of the malignancy by the patient. Involvement of peripheral nerves without the central nervous system involvement has been rarely reported. Perineural tumor spread has been infrequently reported with soft tissue tumors without central nervous system involvement. Here we present an unusual case of an elderly gentleman presenting with symptoms consistent with peripheral neuropathy involving multiple nerves. After failure of symptomatic therapy, electromyogram, and nerve conduction study showed severe bilateral carpal tunnel syndrome. Interestingly, symptoms worsened in the left hand after bilateral release surgery. Due to persistence of significant lifestyle-limiting symptoms, biopsy of the sural nerve was done that showed metastatic poorly differentiated adenocarcinoma cells. A complete surveillance for the primary lesion has been negative so far. The peripheral neuropathy was considered to be arising from the involvement of the perineural sheaths by the metastatic tumor lesions. The patient was then started on gemcitabine therapy and after just 2 cycles of chemotherapy, the patient has shown notable improvement of his symptoms. After completion of the duration of chemotherapy, he has been symptom-free for more than 6 months. Metastatic lesions to the peripheral nervous system should be considered in patients who have persisting neuropathic symptoms because treatment of those lesions can results in improvement of symptoms.