Abstract
A schwannoma is a benign nerve sheath tumour originating from schwann cells. It is the most commonly occurring peripheral nerve sheath tumour. The common sites of occurrence are the head and neck followed by the upper and lower limbs. Diagnosis is straightforward and is made clinically. Schwannomas of the tibial nerve pose a problem. The literature describes them as causes of chronic, intractable lower limb pain because their diagnosis is often delayed for several years. The main reason postulated is that a lump is not always palpable in the early phases and hence chronic cramping pain in the calf or foot is attributed to lumbosacral radiculopathy or local neuropathy.
We report the largest case series of twenty-five patients diagnosed with a tibial nerve schwannoma. Only three cases were diagnosed within a year of initial presentation. The mean time to diagnosis was eighty-six months. The most common site of pain was the sole of the foot (eighteen cases). A Tinel's sign was elicited in nineteen cases. MRI confirmed the diagnosis in all the twenty cases where it was performed. Surgical resection was performed in all cases yielding excellent results. Only one patient required further neurolysis for persisting pain.
In patients with a long history of neuropathic lower limb pain, where lumbar and pelvic lesions have been excluded, a high index of suspicion should be maintained for a peripheral nerve tumour. Delay in diagnosis is commonly due to lack of familiarity with peripheral nerve pathology and the absence of a palpable lump. The delay can result in numerous unnecessary medical and surgical interventions in this group of distressed patients. The Tinel's sign is the key to identifying a tumour of neural origin in the absence of a palpable lump. Surgical resection of the tumour remains safe and effective in providing symptomatic relief.
