Circumferential Adipose Lesion of the Sciatic Nerve.

Area of Science:

• Neurology
• Pathology
• Surgical Oncology

Background:

• Adipose lesions of nerves are classified as extraneural or intraneural lipomas, or lipomatosis.
• Circumferential lipomas completely encircling a nerve are uncommon and poorly understood.
• This case presents an unusual circumferential lipoma of the sciatic nerve.

Observation:

• A 44-year-old woman experienced progressive sciatic neuropathy over one year.
• MRI revealed a large lipomatous mass enveloping the right sciatic nerve.
• The lipoma was surgically resected, resulting in improved neurologic symptoms.

Findings:

• The lipoma completely encircled the sciatic nerve proximally, with partial involvement distally.
• The lipoma was extraneural, not covered by the epineurium.
• Two potential pathogenetic mechanisms were considered: gradual envelopment by an extraneural lipoma or origin within the paraneurial compartment.

Implications:

• This case underscores the underrecognition of circumferential nerve lipomas.
• It highlights the diagnostic and therapeutic challenges posed by complex adipose lesions affecting nerves.
• Further research is needed to elucidate the pathogenesis of these rare tumors.