Hereditary neuropathy prone to pressure paralysis

from Wikipedia, the free encyclopedia
Classification according to ICD-10
G60.0 Hereditary sensorimotor neuropathy
ICD-10 online (WHO version 2019)

When hereditary neuropathy with liability to pressure lesions , also known as HNPP from English "Hereditary Neuropathy with liability to pressure palsies" or as tomaculous neuropathy refers, is a neurological disease from the group of neuropathy (nerve damage).

In the case of HNPP, pressure paralysis of peripheral nerves often occurs even with everyday stress . B. express in numbness, abnormal sensations and weakness. They usually regress after a few days or only a few months.

A demyelination (demyelination) of the nerves shows in electrophysiology a focal slowdown in the nerve conduction velocity up to conduction block. Together with the characteristic anamnesis and the clinical-neurological examination (e.g. failure of the Achilles tendon reflexes ), this leads to a suspected diagnosis. In the nerve biopsy , the nerves are tomacular, i.e. with swollen myelin sheaths that appear sausage-like in their appearance ( Latin tomaculum - sausage, sausage ). These thickenings are often found on Ranvier's tie rings ; on such a lace ring, the subsequent nerve fiber segment is then myelinated much more thinly. The diagnosis can definitely be made using genetic analysis.

Clinical manifestation

Hereditary neuropathies are usually slowly progressive diseases with different ages of onset (with CMT1a in 80% before the age of 20). Patients with CMT 1 and CMT 2 show characteristic distally symmetrical muscle atrophy and paresis of the upper and lower extremities, lost reflexes, foot deformities and gait disorders. Sensitive deficits are present in varying degrees. Dysesthesia does occur. Hereditary demyelinating neuropathy with a tendency to pressure paresis (HNPP) is characterized by the occurrence of recurrent focal pareses (e.g. foot dorsiflexion paresis, hand extensor paresis), which often regress without a residue. Progressive forms with distally symmetrically distributed paresis have also been described. Some neuropathies manifest themselves through additional symptoms such as blindness, deafness, scoliosis, or others, which can provide important clues about the causal genetic defect.

HNPP can have different degrees of severity, but life expectancy is not restricted.

The disease is hereditary. The cause is a deletion or mutation in the gene that codes for the peripheral myeloprotein PMP22 . It is the same gene that leads to HMSN 1A when duplicated . Furthermore, mutations in the gene for the myelin protein zero (MPZ) and in the gene for connexin 32 ( GJB1 ) are often found in demyelinating neuropathies . The latter is coded on the X chromosome, so female carriers are often less affected or even asymptomatic. In recessive, demyelinating neuropathies, mutations of the KIAA1985 gene ( CMT4C ) are found in the German population .

Prognosis and symptomatic therapy

A causal therapy is still not available for hereditary neuropathies. Patients are instructed to avoid triggering situations for the pressure lesions.

After many years of the disease, the ability to walk is restricted, which can vary greatly. With increasing paresis, an optimal supply of aids is to be aimed for: z. B. Foot lifter orthoses, orthopedic shoes, possibly knee orthoses. If the walking distance is restricted, it makes sense to equip it with a stick, rollator and, if necessary, a wheelchair for longer walking distances. Surgical correction can be carried out if the foot is severely deformed. If the hands are severely affected, there is help for writing and eating.

Physiotherapy and, especially in the case of paresis of the hands, occupational therapy should be used regularly for these chronic diseases.

The potential effect of some drugs in inducing or dramatically worsening neuropathy should be considered in patients with hereditary neuropathy. These include u. a. Adriamycin, penicillin in high dosage, gold, amiodarone, phenytoin, lithium, colchicine, vincristine, misonidazole, vitamin B6 high dosage, penicillamine, perhexilenes, hydralazine, chloramphenicol, isoniazid, cisplatin, taxol, dapsone, vitamin A, nitrofurantoin.

Experimental therapeutic approaches

In animal experiments it could be shown that with CMT1a by administration of progesterone receptor antagonists the overexpression of PMP22 could be reduced and the clinical symptoms could be alleviated (Sereda et al. 2003). The administration of ascorbic acid improved the myelination in the CMT1A mouse, decreased the PMP22 expression and led to premature death less frequently (Passage et al. 2004).

literature

  • H. Grehl, C. Moll, C. Meier: Hereditary neuropathy with a tendency to pressure lesions. In: Dtsch Med Wschr. 1987; 112, pp. 254-258.
  • Holger Grehl, Bernd Rautenstrauß: Hereditary motor-sensitive neuropathies: Consequences of molecular genetic findings for diagnosis and therapy. In: Deutsches Ärzteblatt. 94, Issue 19, May 9, 1997, p. A-1275.

Web links