Types of Nerve Bundle Tumors of the Wrist
Schwannomas or neurilemomas are benign solitary tumors common in adults. These tumors usually arise from a single nerve fiber within a bundle and displace the rest of the nerve. However, they can enlarge and involve the rest of the nerve fibers. Schwannomas grow slowly and are usually unnoticed until they enlarge and are accidentally bumped. There are no sensory or motor deficits felt, that is, they are not associated with pain, numbness or weakness of the hand and wrist unless they have become sufficiently enlarged. They can be easily removed surgically, except when they invade other surrounding nerve fibers.
Fibrolipomatous hamartoma is a rare tumor that commonly affects the median nerve, but may also affect the radial and ulnar nerves in the wrist, and other peripheral nerves as well. This tumor is also called fibrolipoma of the nerve. It is a condition where fatty and fibrous tissues invade the outer covering of the nerve. When enlarged, it can cause numbness and weakness of the fingers. The fingers can also appear enlarged. It may occur very early in life (from birth) and up to 30 years or less. Magnetic resonance imaging will show an even distribution of the fatty mass in the fingers or digits, and is often described as “coaxial cable-like" appearance. The condition is benign (no threat to life) but difficult to treat because resection can cause involvement of nerves and lead to sensory and motor deficits. Amputation may be needed if severe deformity exists. Also, recurrence is very common.
Neurofibromas or hamartomas are lesions which are thought to be malformations of the nerves and are not really tumors. They may be solitary, but they usually occur as part of a syndrome called neurofibromatosis or von Recklinghausen disease, where they occur in multiples. Solitary nodules usually occur at a young age. Symptoms include pain and peripheral deficits. Although they are benign, they are difficult to treat surgically because of extensive nerve involvement.
In general, a nerve bundle tumor on the wrist can cause symptoms of nerve compression because of the location and function of the joint. These include pain, numbness and weakness of the fingers, depending on extent of compression on the one or a combination of the three nerves.
However, similar symptoms may be experienced in other types of tumor within the wrist which may likewise cause nerve compression, such as in ganglion cysts and lipomas. These benign tumors do not directly invade the nerves but grow as soft tissue masses that may eventually compress or entrap the nerves and produce similar symptoms. They can also be similar to a condition called carpal tunnel syndrome, which is caused by repetitive movements of the hand, as in people who work in offices or factories.
Diagnosis can usually be made by history, physical examination and laboratory examinations which include ultrasonography, CT scan, MRI and electromyography.
Surgical treatment to remove the tumor is ideal, but in a few cases where there is extensive involvement it may not be very effective.