Edited by Gareth Parry, M.D., FRACP
What Is Hereditary Neuropathy with Liability to Pressure Palsies?
Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) is a progressive neuropathy in which there is also an abnormal sensitivity of the nerves to pressure. This most commonly occurs where nerves pass through restricted anatomic areas, from direct pressure, or from stretch. The pressure can be slight, causing symptoms of tingling, numbness, and weakness. Normal individuals may have similar symptoms with nerve compression but the symptoms last less than five minutes. In persons with HNPP, symptoms occur with minimal pressure and may last much longer, up to several weeks, or months. Pain is not a common symptom, but can occur with acute or cumulative trauma. Recovery is initially complete, but after many recurrences, permanent nerve damage may occur. Severity of symptoms is highly variable, ranging from asymptomatic to severely debilitating, but the majority of people are mildly involved. Symptoms may first appear in childhood, more commonly in teens or twenties, but sometimes not until later in life. It is estimated that 90% of people with HNPP are undiagnosed. HNPP is inherited as an autosomal dominant trait. It is characterized by sausage like thickenings of the myelin sheath around the peripheral nerves. This thickening contributes to an abnormal sensitivity to pressure on the nerves.
Treatment options are limited.. The primary treatment is to prevent nerve injury by avoiding pressure or nerve stretch. The most commonly effected nerves are those that are frequently subject to compression neuropathies in the general population. These include the median, ulnar and radial nerves in the arm and the peroneal nerve in the leg. These are related to compression of a nerve between a hard surface and bone, under a fibrous band, scar tissue, abnormal muscles or from swelling inside a tunnel due to overuse. The brachial plexus may also be affected, perhaps because of its susceptibility to stretch injury. When nerves are entrapped at the sites listed above, surgical decompression is often recommended, but it's efficacy is limited and it is often poorly tolerated.
Principles of management
The principles of conservative management for HNPP are similar to any entrapment neuropathy. These have been developed through the study of ergonomics, which is concerned with the design of the workplace, tools, and tasks to match the worker. These principle can be applied to any task at home as well as in the work setting.
1)Reduction of extreme or awkward joint position, by bending the tool or handle instead to the joint, moving the part so the joint can remain straight, or changing your body position in relation to the part.
2)Reduction of excessive force and static holding by keeping cutting edges sharp, using power tools instead of manual force, using clamps to stabilize parts instead of hand. Spread the force, using stronger muscles, two hands instead of one, and tools with handles that comfortably fit the hand. Get close to the object or activity, with your arms comfortably at your sides.
3)Reduce repetition by varying tasks, staggering repetitive activities throughout the day, allowing adequate rests breaks, mechanizing whenever possible.
Other important factors in management of HNPP are pacing to avoid overfatigue, and maintaining general fitness and flexibility. The nervous system is a dynamic, interconnected system. Restriction in its ability to glide within the body in response to position changes increases the tension and susceptibility to compressive forces. Entrapment of a nerve at one site also makes it more susceptible to entrapment at other sites.
Different nerves have multiple sites of potential entrapment with different movements and postures that contribute to the compression.
The Brachial Plexus is a network of nerves running between the neck and the shoulder. It can be irritated at multiple areas, including where it passes through muscles in the front and side of the neck (scalenes), between the collarbone and first rib, and under a muscle in the chest area (pectoralis minor) which pulls your shoulder blade forward. This may be more related to stretch than compression.
Symptoms can be variable depending or the part of the plexus that is compressed. It can result in numbness and weakness of the entire arm. The space the nerves pass through can become constricted due to tight muscles in the front of the neck from poor posture or use of scalene muscles for breathing which then also elevates the first rib. Forward shoulder posture allows the pectoralis minor muscle to tighten. The muscles in the front of neck are frequently strained in whiplash injuries. Activities that involve repetitive or sustained overhead use of arm, forward reaching, or excessive weight on the shoulder can cause symptoms. Waking with arms numb from sleeping with arms overhead is common.
Ways to avoid brachial plexus compression include:
1)Maintain flexibility of neck, upper back, and shoulder area.
2)Maintain good posture, by tilting your pelvis forward and lifting your chest, not by pulling your shoulder blades back. Your shoulder blades fall into the correct position if your trunk is aligned right.
3)Breath with your diaphragm, not your upper chest muscles. Your abdomen and lower rib cage should go in and out when you breath, which also helps control levels of muscle tension.
4)Avoid repetitive or sustained overhead work or sleeping with arms overhead.
5) Avoid carrying heavy bags on your shoulder, including purses, especially with narrow shoulder straps. Use a luggage carrier on wheels instead for heavy loads or a fanny pack.
6) If you work at a desk, place objects within close reach, with chair set up so your elbows are held at about a right angle, shoulders hanging relaxed at your side, wrists in neutral position, feet supported on floor or foot rest, if needed to keep the hips and knees at about 90 degrees.
7)A slanted work surface and/or book or document holder may facilitate better posture while writing. If you have already had brachial plexus compression, it is best to consult a medical professional such as a physical therapist or occupational therapist, who can evaluate you to determine the specific exercises you should do. If your first rib is already significantly elevated, working on stretching your shoulders and vigorously correcting your posture can increase your symptoms so the rib elevation needs to be addressed first.
The median nerve can be compressed at the wrist where it passes through the carpal tunnel, along with nine finger flexor tendons. Stressing and irritating the wrist and tendons can cause swelling around the tendons, putting pressure on the median nerve and resulting in numbness, tingling and pain in the palm side of the thumb, index and long fingers and weakness of the small muscles that control the thumb. Anything that causes swelling, including pregnancy, some types of arthritis, or previous wrist fractures can contribute to the development of carpal tunnel syndrome (CTS). Repetitive pinch or gripping, especially with force, and while bending the wrist are primary causes of CTS. Management and prevention includes use of wrist splints at night to keep wrists in a neutral position. These are also sometimes recommended during the day during work activities. Wrist splints occasionally make HNPP patients worse, possibly related to fighting against them. Avoid repetitive gripping or pinching, especially with the wrist bent. Use power jar openers, can openers, larger handled tools, larger diameter pens or pen grips for writing to reduce stresses. Using knives with angled handles can help keep wrists in neutral with cutting and chopping activities in the kitchen. Using food processors and mixers also are of benefit. Different computer keyboards are now available to help maintain wrists in a more neutral position, including the Microsoft Wave keyboard.
Decompression surgery can help in HNPP, but it's effect is often short lived (2-3 years); and re-operation is usually unhelpful and may even increase the nerve damage.
The ulnar nerve can be compressed/stretched as it passes in a bony groove behind the elbow and where it dives under a wrist flexor muscle. Compression cause numbness and tingling of the small and ½ of the ring finger, and the front and back of the small finger side of the hand. It can cause weakness of the small muscles of the hand, with clawing of the ring and small fingers and weakness of grasp. Compression is caused by sustained or repetitive bending of the elbow greater than 90 degrees or habitual leaning on elbows. Avoiding resting on your elbow, using elbow pads to reduce pressure, and using elbow splints to keep you from bending your elbows while sleeping can prevent problems. You can wrap a towel around your arm at night to keep it from bending, or it that does not work, a hand therapist can make a splint for you. Using head phones can reduce stresses during phone use and using a pillow to support a book can help while reading.
The ulnar nerve can also be compressed where it, passes through a tunnel in the heel of the hand. Compression in this area causes weakness of the small muscles of the hand, usually without sensory symptoms. It is caused by repetitive or sustained forces to the heel of the hand or wrist held in hyperextension in activities such as riding a bike, using a cane or walker, doing pushup and weight lifting. Ways of avoiding stress include riding bike in a more upright position (low positioned handles may need to be modified), minimizing the weight on your hands, using biking gloves, using a cane with a broader handle, using alternative equipment for strengthening that does not cause stress through your hand.
The radial nerve can be compressed in the posterior upper arm where it lies close to the humerus, causing wrist drop and numbness and tingling in the thumb side of the back of the wrist and hand. This can be caused by resting the upper arm on a firm object like the back of a chair, incorrectly using crutches, or your partner or a baby resting their head on your arm. Avoid resting your upper arm on the back of a chair, over the edge of the bed, or allowing your partner to rest their head on your arm. When using crutches, the top of the crutch should be supported against your chest wall. You should not weight bear though the arm pit area.
The radial nerve can also be compressed in the back of the forearm at a couple of places where it passes under the supinator muscle (rotates palm up), or wrist and finger extensors. Compression of the superficial branch of the nerve causes numbness and tingling on the back of the hand. Compression of the deep branch (posterior interosseous) leads to weakness of the muscles that straighten the wrist, fingers and thumb. It occurs as the result of forceful twisting palm up, wrist extension and deviation to thumb side. It can also be caused by carrying heavy items on the forearm or straps from heavy bags putting pressure on the forearm. Using power screwdrivers, power jar and can openers, power mixers, avoiding hanging bags over your forearms, using wheeled luggage carts can help reduce stresses. Also avoid sports like tennis or racquet ball.
A small sensory branch of the radial nerve can be compressed at the wrist, causing numbness on the back of the thumb, index, and long fingers. This is often caused by tight wrist bands. Avoiding clothing that is tight at the wrist, wearing tight watch bands or bracelets, or carrying bags hanging from a strap around the wrist can prevent this.
Small digital nerves to the fingers and thumb can be compressed by tight rings and by use of scissors. Have your rings sized correctly and use scissors with larger handles, self opening handles, or an electric scissors.
In the lower extremity, the sciatic nerve can be compressed from prolonged sitting on a hard surface, sitting on a chair with too short or too long a seat, with sharp edges, or by sitting, cross legged for prolonged periods. A complete sciatic nerve compression leads to weakness of the knee flexors and all muscles below the knee. Fortunately this is rare, and can be avoided by frequent positions changes, choosing a seat that ends 1-2 inches from the back of the knee, and slopes gently down at the front edge. Using a portable seat cushion can help when the only seating option is a hard surface like bleacher seats.
Entrapment of the common peroneal nerve is the most frequent entrapment neuropathy in the leg, particularly, in the region of the fibular head on the outside of the knee. This leads to a foot drop and numbness over the outside of the lower leg and on the top of the foot. Pressure can come from crossing legs or recurrent stretch injury as a result of an unstable ankle. Knee high stocking that are too tight and casts for fracture immobilization can also cause compression. Avoidance of crossing your legs and tight stockings pan help prevent this. Also use of a lower leg brace (prescribed by your physician), or high top shoes can help stabilize the ankle once weakness has occurred, as the ankle instability caused by the weakness can contribute to reinjury.
Entrapment of the posterior tibial nerve can occur below and behind the medial malleolus on the inside of the ankle. Flat feet with overuse of stabilizing muscles whose tendons pass through the area can contribute to this. Well fitting, possibly custom arch supports can reduce this problem.
Digital nerves to the foot can be compressed by tight shoes. Choose comfortable, well fitting shoes.
Pacing is a critical aspect of symptom management, particularly when you have started to develop a peripheral neuropathy. With any nerve related weakness, it is very easy to over fatigue the muscles, leading to problems with joints, ligaments and possibly causing muscle damage and further weakness. When a muscle fatigues, and can no longer perform it's function, you are more likely to change the way you do things to continue the activity, overusing other muscles and possibly causing more nerve compression problems.
Pacing may involve spreading more difficult tasks out over the day, week and month. Depending on the severity of the symptoms, it may also involve eliminating some more difficult tasks or delegating them to others. You need to spend some time listing all the activities that you need to do and want to do on a daily, weekly, monthly and yearly basis. These activities then need to be prioritized, by what is essential versus optional and whether any of the activities can be delegated on a regular basis to family members or hired out. Make sure that something you enjoy is included in the list of essentials, Then you need to spread those activities out over the course of the week so you are not doing all the stressful activities in one day such as cleaning the house, washing clothes and shopping. Sometimes it seems more efficient to bunch activities, but when you become overtired and then can't function at all for a couple for days, you get a lot less done.
As you schedule your day, you also need to schedule in breaks. It is better to schedule short breaks frequently, before you get tired, than a longer one once you are already tired. How long and how frequent the breaks are is dependent on the severity of your condition and needs to be determined by your symptoms.
Pacing may also involve accepting use of different assistive devices, such as canes, walkers, braces or a motorized cart. Expending all your energy in getting from one place to another so that you have to significantly limit your activity is a high price to pay for pride or vanity.
Pacing also needs to be considered with your exercise program. Exercises need to fit into your life, can't be so extensive that you have no energy for anything else, but also need to address your specific problems. Maintaining a strong flexible body can help increase your tolerance for stressful activity. If you are already having problems, you need to start an exercise program to increase your flexibility, strength and endurance, but it needs to be done cautiously, avoiding over fatigue and over straining the muscles and nerves. The nerves in particular need to the respected, as symptoms may not be noticed while you are doing the activity, but later. The exercise philosophy of "No Pain- No Gain" is definitely NOT appropriate for persons with HNPP. Starting with a low impact program with focus on posture, breathing and relaxation and slow controlled movements is the safest approach. Activities such as water exercises and Tai Chi done in a pain-free range can be of benefit. There may be specific areas you need to address, but this is best done with the input of a health professional familiar with your condition and knowledgeable about exercise.
Although there is no cure for HNPP, symptoms are best manages by avoiding the activities and postures that cause them. You may have to significantly limit your activities initially Once you have stopped the downward spiral , or the continuous up and down cycle, you can try and gradually increase your activity again, slowly enough to avoid over fatigue. With pacing, hopefully you will find an increase in energy and gradually increasing tolerance for activity.
Last updated: 9/99
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