[Pisio-hamate hiatus syndrome]

Area of Science:

• Neurology
• Hand Surgery
• Nerve Compression Syndromes

Background:

• Ulnar nerve entrapment can cause intrinsic hand muscle weakness.
• Idiopathic cases without clear etiology or sensory loss present diagnostic challenges.

Observation:

• Two patients presented with progressive intrinsic hand muscle atrophy, excluding the abductor digiti quinti.
• Neurological and neurophysiological exams localized the lesion to the deep branch of the ulnar nerve.
• Surgical exploration revealed nerve enlargement at the pisohamate hiatus, with one case showing possible neoplastic changes.

Findings:

• Histological analysis in one case indicated chronic compression with interneural fibrosis and axonal loss, rather than neoplastic or inflammatory changes.
• Surgical decompression and nerve grafting in one case, and tenolysis in the other, yielded poor outcomes due to delayed treatment (10 and 3 years post-symptom onset).

Implications:

• This case series underscores the potential for chronic compression to cause significant ulnar nerve damage.
• Delayed surgical intervention in ulnar nerve entrapment significantly compromises functional recovery.
• Early diagnosis and treatment are crucial for managing intrinsic hand muscle weakness caused by ulnar nerve compression.