Preserved Neurologic Function following Intraneural Fascicular Dissection and Nerve Graft for Digital and Median Nerve Lipofibromatous Hamartoma

Abstract

Sir: A 35-year-old, right-handed woman complained of an enlarging, painful right palmar mass of 6 months' duration. The lesion was palpable between the distal palmar crease and the base of the right fourth metacarpophalangeal joint. There was no history of trauma and no motor or sensory deficit. She underwent carpal tunnel release and intraneural fascicular dissection of the median nerve with extension into the common digital nerve of the ring finger (Fig. 1, above).Fig. 1.: Intraoperative images of the lipofibromatous hamartoma. (Above) In the first operation, a Brunner incision proximal to the wrist crease and distal to the distal interphalangeal joint of the ring finger exposes the mass. (Below) In the second operation, reexcision and cable nerve anastomosis using a sural nerve graft are performed.Histologic evaluation demonstrated a 5-cm median nerve lipofibromatous hamartoma (Fig. 2). She had preserved motor function and sensation at 6 months.Fig. 2.: (Above) S-100 staining. (Below) Hematoxylin and eosin staining. There is increased mesenchymal tissue around the myelinated areas. There are fatty deposits within the nerve section.Two years later, reexcision and cable nerve anastomosis were performed using sural nerve graft for tumor recurrence (Fig. 1, below). No postoperative motor deficits have been documented. She recovered her protective sensation by 6 months and remains recurrence-free at 3 years. Lipofibromatous hamartoma is a rare benign tumor most commonly involving the median nerve.1–4 However, radial nerve, ulnar nerve,5 superficial peroneal nerve,6 plantar nerve,7 and brachial plexus involvement may be found (Table 1).8Table 1: Summary of Findings in a Report of 18 PatientsThe cause is unknown. Although believed to be a congenital lesion, lipofibromatous hamartomas usually present in the third and fourth decades of life. Abnormal development of flexor retinaculum in childhood,9 a history of trauma,10 and chronic nerve irritation have been postulated as possible causes. It is most common among Caucasians. One-third present with macrodactyly, which is unilateral 90 percent of the time.8,11 Girls are more commonly affected when macrodactyly is present. The upper extremities are affected three times more frequently than the lower extremities. Clinically, the tumor often presents with digital enlargement at birth12,13 or swelling or mass on the volar aspect of the distal upper extremity. The mass usually appears without neurologic symptoms.14 Magnetic resonance imaging is useful for diagnosis and surgical planning.15 T1-weighted images show similar signal intensity to muscle, whereas T2-weighted images show heterogeneous signal intensity with focal areas of high signal.15 A characteristic feature is the serpentiform nerve fascicle appearance, surrounded by fibrofatty tissue within the nerve sheath.16 On coronal images, a spaghetti-like appearance of the nerve is pathognomonic.17,18 Electrophysiology is used to evaluate the functional compromise and gives a baseline if surgery is contemplated.19 The diagnosis is supported with tissue biopsy. The differential diagnoses include intraneural lipomas, hereditary hypertrophic interstitial neuritis, neurofibromas, neurilemomas, and isolated macrodactyly.9,10,20 The term “hamartoma” is used because of overgrowth of normal fat and fibrous tissue.8,13,20 It is a well-encapsulated, yellowish, fusiform enlargement of the nerve. It is not usually adherent to adjacent tissues.1 Microscopic examination reveals epineural, perineural, and perivascular fibrosis, making the dissection technically challenging. Postoperatively, sensation is often diminished. Surgical options include decompression of surrounding tissues, decompression and debulking of the fibrofatty sheath,4,10,14,21 microsurgical nerve dissection, and excision with or without grafting.8,22 Radical surgery is usually unnecessary.3,14 Function can be preserved using microsurgical dissection and cable grafts if distal sensation remains intact. Julio A. Clavijo-Alvarez, M.D., Ph.D. Division of Plastic and Reconstructive Surgery University of Pittsburgh Medical Center Pittsburgh, Pa. Melissa Price, B.S. Guy M. Stofman, M.D. Plastic and Reconstructive Surgery University of Pittsburgh Medical Center Mercy Hospital Pittsburgh, Pa.