Fibrolipomatous nerve tumours are rare benign tumours that are usually slowly progressive and that predominantly affect the median nerve at the level of the wrist and hand, usually causing carpal tunnel syndrome.1 The tumour is sometimes associated with macrodactyly and lipomatous macrodystrophy of muscles and subcutaneous fat in the region supplied by the affected nerve.1 2 In this report we focus attention on fibrolipomatous hamartoma at a previously undescribed location as an unusual cause of cubital tunnel syndrome. Furthermore, we point out that on the basis of the characteristic features of fibrolipomatous hamartoma on MRI, a non-invasive diagnosis can be made.

The 35 year old female patient was born with a giant fourth finger (about twice as thick as the neighbouring fingers) of the right hand which grew proportionally with the other fingers during early childhood. The family history was unremarkable. For cosmetic reasons, the finger was amputated at the age of three. When the patient was 27 years old, she experienced hypaesthesiae and paraesthesiae in the cutaneous area of the right ulnar nerve and a stabbing pain in the ulnar arm. She also noticed a slight weakness in the flexion of the fourth and fifth fingers, of wrist flexion, and flexion of the hand muscles innervated by the ulnar nerve. At the same time she noticed a thickening of the ulnar nerve at and above the elbow, with electrical sensations elicited by nerve percussion. …