Hereditary Neuralgic Amyotrophy – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY

Excerpt

NOTE: THIS PUBLICATION HAS BEEN RETIRED. THIS ARCHIVAL VERSION IS FOR HISTORICAL REFERENCE ONLY, AND THE INFORMATION MAY BE OUT OF DATE.

Clinical characteristics: Hereditary neuralgic amyotrophy (HNA) is characterized by sudden onset of severe, non-abating pain in the shoulder girdle and/or the upper limb and amyotrophy (muscle wasting or atrophy) that typically develops within two weeks of the onset of severe pain. Other sites may also be involved in an attack; sensory symptoms, present in the majority of affected individuals, can include hypoesthesia (decreased sensation) and paresthesias. Onset is typically in the second or third decade (median age 28 years). Although attacks appear to become less frequent with age, residual deficits accumulate with subsequent attacks. In some families, non-neurologic findings (characteristic craniofacial features, bifid uvula or cleft palate, short stature, and/or partial syndactyly of the fingers or toes) are present.

Diagnosis/testing: The diagnosis of HNA is based on clinical findings. SEPTIN9 (formerly SEPT9) is the only gene in which pathogenic variants are known to cause HNA; however, genetic heterogeneity exists.

Management: Treatment of manifestations: Pain management is the primary goal of therapy and varies between acute and chronic stages. Corticosteroids have been used in the acute phase to shorten the duration of pain and improve recovery. Consultation with a physiatrist is recommended for chronic pain and persisting paresis. Patients with phrenic nerve palsy need specialized respiratory consultation and can benefit from noninvasive nocturnal positive pressure ventilation. Cleft palate is managed by standard protocols.

Surveillance: Follow up every six to 12 months after the initial diagnosis to identify chronic pain resulting from altered biomechanics of the shoulder or arm.

Agents/circumstances to avoid: Overexertion of a limb with persistent weakness, especially if the scapula is unstable.

Genetic counseling: Hereditary neuralgic amyotrophy is inherited in an autosomal dominant manner. Most individuals diagnosed with HNA have an affected parent; the proportion of cases caused by a de novo pathogenic variant is unknown. Each child of an individual with HNA has a 50% chance of inheriting the pathogenic variant. Prenatal diagnosis for pregnancies at increased risk is possible if the pathogenic variant in the family is known.