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Neuropathia hereditaria motoria et sensoria
The commonest inherited nerve disease: it progresses slowly, and stretching, splints and balance keep independence for a long time.
Also known as: Hereditary motor and sensory neuropathy · HMSN · peroneal muscular atrophy · CMT1A · PMP22 duplication
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.
The commonest inherited nerve disease — about one in 2500 to 3300 people. Unlike HNPP, where nerves fall asleep under pressure, here a slowly progressive weakness dominates, starting in the feet and moving upward over years. The order is typical: first a high arch (pes cavus) and claw toes, then difficulty lifting the foot, so the toes catch when walking — often with frequent tripping and ankle twists. Because the calves waste while the thighs stay strong, the picture of “stork legs” appears. Reflexes are reduced and sensation in feet, later hands, is mildly to moderately diminished; fine hand function usually follows only years later. Onset is mostly in the first to third decade. Inheritance is predominantly autosomal dominant; recessive and X-linked forms exist. The commonest subtype is CMT1A, caused by a duplication of the PMP22 gene — the same gene that is missing in HNPP, here in excess. About a third of cases arise anew, without affected parents. Assessment is two-stage as in HNPP: nerve conduction velocity (clearly slowed in CMT1, below about 38 m/s), then genetic testing starting with the PMP22 duplication. There is no causal cure so far; what is well established is that physiotherapy, fitted orthoses and foot care preserve mobility and independence for a long time. Life expectancy is as a rule normal. Two points are worth knowing: some nerve-damaging drugs should be avoided or medically reassessed, and fall prevention is a worthwhile topic in its own right.
Regular stretching counters the shortening that worsens the high arch and toe-down position. Preserving mobility is the best-supported lever.
A fitted orthosis lifts the toes when walking — markedly fewer trips and falls, and longer distances become possible again. Fitting by specialists.
With reduced sensation, pressure points and small wounds are easily missed. Check feet daily, soft seams, room for the toes, and caution with hot water bottles.
As strength and position sense decline, balance is a training goal in its own right. Removing trip hazards at home and lighting the night route belong here too.
Moderate endurance and strength preserve function. Very hard, exhausting loading of weakened muscles is rather unfavourable — set the dose with physiotherapy.
Some agents, especially certain chemotherapies, can further damage nerves. The diagnosis therefore belongs in every treatment plan — do not stop anything on your own.
When buttons, zips or keys get harder, aids and techniques often help more than strength training alone.
Because the trait is usually passed on dominantly, the diagnosis also concerns relatives. Counselling puts it in context without pressure — the decision stays with each person.
There is so far no drug that halts the nerve remodelling in CMT. What changes daily life is mechanical: an ankle-foot orthosis holds the foot while walking and prevents tripping — the single most effective measure. Physiotherapy maintains movement; moderate strength training is useful, overloading is not. Certain drugs are unfavourable in CMT, among them vincristine — that belongs in every consultation, because otherwise it goes unnoticed.
About one in 2500 people is affected — making it the most common inherited nerve condition. The first signs usually show in the first two decades: high arch, hammer toes, frequent ankle turns. The course is slow over decades; life expectancy is normal in the common forms. About one in four needs an ankle-foot orthosis over time. Nerve conduction speed separates the subgroups and in the most common form is under 38 metres a second.
A strikingly high instep, toes that claw, and shoes worn down on one side of the heel — often already in youth, long before anyone speaks of weakness.
Tripping on the edge of a carpet, an audible slap of the foot when walking, frequent turning of the ankle. The weakness starts at the feet and slowly moves upwards over years.
The calf muscle shrinks while the thighs stay normal — a picture often compared to an upturned champagne bottle.
Numbness and an unsure feeling in the dark, because the feedback from the feet is missing. Burning pain rather does not belong to it — that points to other kinds of nerve disorder.
Not proof of CMT — used to exclude and to spot an additional, treatable nerve burden.
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.
The same rule as with all hereditary nerve conditions: B6 in high dose over months damages nerves, and here there is little reserve to begin with. Normal amounts inside a complex are no issue — the 100 and 200 mg preparations are.
The foot-drop weakness makes falls more frequent, and over the years bone density becomes the real question. Vitamin D, calcium and — as far as possible — loading the bone are the counter-direction here.
Tested several times in hereditary nerve conditions. The studies found no reliable gain in strength — unlike in healthy muscle, where the effect is well established. That is the difference between a muscle that can be trained and one that is no longer properly commanded.
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.
Before a hereditary nerve condition is assumed, the fixable causes belong off the table: underactive thyroid, B12 deficiency, sugar. They make a similar picture and can be treated — that is the reason they are checked first.
If diabetes comes on top of a hereditary neuropathy, the damage adds up on the same nerve. This is why the sugar value counts more here than in someone with healthy nerves — it is a question of the sum.
With an existing nerve disease high-dose B6 can worsen the damage. Above 50 mg a day over longer periods counts as critical — rarely stated on the packet.
Weakness in feet and lower legs makes every extra kilo noticeable. Keeping weight in range eases walking more than any supplement.
Moderate training preserves the strength that remains. Very intensive strength training is not recommended — it can further damage already weakened muscle.
Here mainly as a warning: with an existing nerve disease high-dose vitamin B6 can worsen the damage. Above 50 mg a day over months counts as critical — many combination products exceed that.