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Neuropathia hereditaria cum paralysibus a pressione
The nerves are built more sensitive to pressure — which is why they fall asleep from everyday things, and why relief is the actual treatment here.
Also known as: Hereditary neuropathy with liability to pressure palsies · tomaculous neuropathy · PMP22 deletion
Open in the tool — with search and all the links →This compilation is for information and replaces neither medical diagnosis nor treatment. If you have symptoms, see a doctor.
A rare inherited feature of the nerves’ insulating sheath: everyday pressure alone makes individual nerves “fall asleep” — far faster and for longer than in other people. Typical are episodes of numbness, tingling and genuine weakness exactly where nerves run close under the skin over bone: foot drop after kneeling or sitting cross-legged, numb fingers and a weak hand after leaning on the elbow, a “wrist drop” after a night with the arm over a chair back, or a carpal-tunnel-like picture. Episodes last minutes to months and usually resolve: about half recover completely, most of the rest keep only mild residual symptoms. The cause is almost always a missing copy of the PMP22 gene, inherited in an autosomal-dominant way — one affected parent is enough, and families often report similar stories that were never explained. Onset is usually at puberty or in young adulthood, but can occur at any age. Assessment has two steps: first nerve conduction studies (electroneurography), which show typical findings even in symptom-free nerves, then genetic testing for the PMP22 deletion. Important: blood tests do not prove HNPP — they serve to rule out commoner causes of numbness. Treatment targets not the cause but the pressure: relief, padding and adapted habits. Life expectancy is not reduced. Two practical points: mention positioning before surgery, and medical caution applies with certain drugs.
At the elbow the ulnar nerve lies almost unprotected on bone. Leaning on a table, car door or while phoning is a common trigger for numb fingers and a weak hand.
At the outer knee the peroneal nerve runs just under the skin — pressure there is the classic trigger of foot drop. Squatting, gardening and tight boot tops count too.
Keeps the wrist neutral and takes pressure off the median nerve — helpful if fingers are numb at night or on waking. Have it fitted medically.
It is not the activity that harms but holding one position for long. Frequent small position changes, breaks during repetitive work and a soft surface relieve the tight spots.
Heavy straps can press on the shoulder’s nerve plexus. Wide, padded straps and spreading the load help.
Under anaesthesia the protective reflex to shift position is absent. Telling surgery and anaesthesia allows targeted padding — the same applies to casts and long procedures.
Some agents can put additional strain on peripheral nerves. Do not stop anything on your own — the list belongs with the treating doctor.
Without the diagnosis a recurring carpal tunnel picture is sometimes operated on when relief would be the better route. The information also matters for relatives, since the trait runs in families.
There is no treatment for HNPP. What counts is avoiding pressure — not leaning on the elbows, not crossing the legs, watching positioning during surgery and in a plaster cast. After a pressure injury the nerve recovers over days to weeks, over months with a stronger injury. Vincristine and some other drugs are unfavourable with this predisposition; that belongs on the emergency card, because otherwise nobody knows.
About two to sixteen per hundred thousand people are affected; the change is passed on by one parent, and about one in two children inherits it. The first episode usually comes between ten and thirty, often after a night in an unusual position or after long sitting with crossed legs. Recovery takes days to weeks, months with more marked damage. In some, remnants stay after several episodes.
A foot asleep after ten minutes of kneeling, a numb arm after a night on one side — and it takes hours to days to come back. In others it is over in minutes.
The foot no longer lifts properly and drags, the hand can no longer grip firmly. That the strength is involved sets the picture apart from an ordinarily numb limb.
Outside of the knee (head of the fibula), inside of the elbow, wrist, shoulder under a rucksack: where nerves run just under the skin over bone.
It is passed on dominantly — parents, siblings or children often report the same episodes, usually without ever having heard a name for it.
Not proof of HNPP — used to exclude: B12 deficiency causes similar symptoms and is treatable.
Without B12 the insulating layer of the nerves is not maintained. A lack causes tingling, numbness and unsteadiness in the dark — and it is one of the few reasons for nerve trouble that can be fully undone if found early.
The nerves cover their energy needs through thiamine. It runs short with alcohol, after stomach operations, with long-lasting vomiting and under water tablets.
Here both count: a lack harms the nerves, and too high an intake over months harms them as well. Supplements therefore belong taken in a dose that has a reason.
Works together with B12. Given alone, folate can improve the blood count while the B12 deficiency goes on damaging the nerves — which is why both are looked at together.
With a hereditarily sensitive nerve sheath everything that additionally burdens nerves weighs double. High-dose B6 is the best known avoidable trigger of nerve damage — described from about 50 mg daily over months, faster in high-dose preparations. A complex in normal amounts is unproblematic.
No influence on the nerves themselves. The reason is a different one: whoever stumbles more often falls more often — and bone density then decides whether a fall stays without consequence.
Clearly worthwhile and well supported when deficient — vegan, older adults, certain drugs. No energy boost without a deficiency.
In pregnancy clearly established against neural-tube defects, otherwise mainly with deficiency. Can mask a B12 deficiency — watch both.
An underactive thyroid makes tissue swell in the narrow nerve canals and produces the same picture — nerves that fall asleep easily, carpal tunnel, tingling. It is treatable and therefore belongs checked first.
Unlike with an inflammation cortisone does not help here — the nerve is pressed, not inflamed. What helps is avoiding pressure: not leaning on the elbows, no tight straps, not crossing the legs.
The nerves react sensitively to pressure. Marked underweight removes the protective fat pad at elbows and knees — one of the few points where diet plays a part here.
Here it is about avoidance: no long positions with pressure on elbows or knees, padding at the workplace. Vigorous stretching with traction on the nerve is rather harmful.