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How does one recognize and diagnose hereditary neuropathy with liability to pressure palsies (HNPP)?
Hereditary neuropathy with liability to pressure palsies (HNPP) also called recurrent pressure-sensitive neuropathy or tomaculous neuropathy, is readily identified in cases of recurrent compression-induced painless mononeuropathies and in patients with autosomal dominant familial patterns, demyelinative features on electrophysiologic studies, and “sausage-shaped” swellings or tomaculi on nerve biopsy.
However, a traumatic or compression-induced mechanism is not always obvious, and the pathologic evidence of numerous tomaculi may be the only diagnostic clue in sporadic cases presenting with a generalized polyneuropathy.
Demonstrating PMP22 gene deletion confirms the diagnosis. The most common nerves affected are the fibular and ulnar nerves.
Generally mononeuropathies spontaneously resolve within days or weeks and recovery is complete 50% of the time.
Electrophysiologic studies show prolonged distal motor latencies, especially involving the median and fibular nerves.
Conduction block and focal motor slowing are noted at entrapment sites during an attack.
Sources
- Immunotherapy for IgM anti-myelin-associated glycoprotein paraprotein-associated peripheral neuropathies. Cochrane Database of Syst Rev (5):CD002827, 2012.
- Nobile-Orazio E: Chronic inflammatory demyelinating polyradiculoneuropathy and variants: Where we are and where we should go. J Peripher Nerv Syst 19: 2-13, 2014.
- Saperstein DS: Chronic acquired demyelinating polyneuropathies. Semin Neurol 28:168-184, 2008.
- Rossor AM, et al: A practical approach to the genetic neuropathies. Pract Neurol 15:187–198, 2015.
