In this disorder, nerves are easily damaged by slight pressure or injury or by repetitive use.
Numbness, tingling, and weakness occur in the affected area.
Electromyography and genetic testing help establish the diagnosis.
People should avoid or modify activities that cause symptoms, and wrist splints and elbow pads may help by reducing pressure on the affected nerves.
(See also Overview of the Peripheral Nervous System Overview of the Peripheral Nervous System The peripheral nervous system refers to the parts of the nervous system that are outside the central nervous system, that is, those outside the brain and spinal cord. Thus, the peripheral nervous... read more .)
In this hereditary neuropathy Hereditary Neuropathies Hereditary neuropathies affect the peripheral nerves, causing subtle symptoms that worsen gradually. (See also Overview of the Peripheral Nervous System.) Hereditary neuropathies may affect... read more , peripheral nerves Overview of the Peripheral Nervous System The peripheral nervous system refers to the parts of the nervous system that are outside the central nervous system, that is, those outside the brain and spinal cord. Thus, the peripheral nervous... read more are susceptible to damage resulting from relatively slight pressure or injury or from repetitive use.
Usually, this neuropathy starts during adolescence or young adulthood, but it may start at any age. It affects both sexes equally.
Hereditary neuropathy with liability to pressure palsies is usually inherited as an autosomal (not sex-linked) dominant trait Dominant disorders Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body or code for functional RNA molecules.... read more . That is, only one gene from one parent is required for the disease to develop.
In this neuropathy, nerves lose their myelin sheath (called demyelination Overview of Demyelinating Disorders Most nerve fibers inside and outside the brain are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation... read more ) and do not send nerve impulses normally. (The myelin sheath functions somewhat like insulation around electrical wires, enabling nerve impulses to travel quickly.)
Symptoms of HNPP
Hereditary neuropathy with liability to pressure palsies commonly affect nerves that run close to the body’s surface near a bone. For example, the following nerves are often affected:
Numbness, abnormal sensations (such as tingling), or weakness occurs periodically in the affected area. For example, peroneal nerve palsy weakens the muscles that lift the foot. As a result, people cannot lift the front part of their foot (a condition called footdrop) and may drag the front part of the foot along the ground as they walk.
Symptoms vary from unnoticeable and mild to severe and incapacitating. Episodes may last several minutes to months. They may recur, sometimes involving different nerves.
After an episode, about half of affected people recover completely, and most of the rest have mild symptoms.
Diagnosis of HNPP
Electromyography and nerve conduction studies
Doctors may have difficulty diagnosing hereditary neuropathy with liability to pressure palsies because the symptoms come and go. Electromyography, nerve conduction studies Electromyography Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Imaging tests commonly used to diagnose nervous system (neurologic) disorders... read more , and genetic testing help establish the diagnosis.
Rarely, biopsy of a nerve is required to look for areas of swelling along the nerve that typically occur in hereditary neuropathy.
Treatment of HNPP
Avoidance of activities that cause symptoms
Wrist splints and elbow pads
Activities that cause symptoms should be avoided or modified.
Supports, such as wrist splints and elbow pads, can reduce pressure, prevent reinjury, and allow the nerve to repair itself over time.