Scalpel Sign in Spine Pathology: Presentation in 3 Different Rare Diagnoses

BACKGROUND: The scalpel sign is a radiological an indentation in the dorsal aspect of the spinal cord resembling a surgical scalpel blade. It is said to be a pathognomonic imaging discovery linked to dorsal arachnoid webs. However, other spine-related conditions may mimic dorsal arachnoid webs on magnetic resonance imaging, such as spinal arachnoid cysts or ventral spinal cord herniation, leading to misdiagnosis. METHODS: A retrospective review was performed of cases involving 3 different diagnoses at our institution in the last 5 years that shared in common the characteristic focal dorsal indentation of the spinal cord. RESULTS: Of 7 cases identified, all but 1 were treated and confirmed intraoperatively. All lesions were located at the dorsal spinal cord. Magnetic resonance imaging was the study of choice for evaluation. Clinical manifestations included back pain and lower extremity numbness and weakness together with compressive myelopathy signs and urinary symptoms. Mean follow-up was 16.8 months with satisfactory postoperative results. CONCLUSIONS: Isolated radiological presentation of the arachnoid webs, arachnoid cysts, and ventral herniation of the spine. However, awareness of its importance is relevant for accurate curative surgical planning.

Automated summary

The scalpel sign is a characteristic radiological finding related to dorsal arachnoid webs. However, other spine-related conditions may mimic this sign, leading to misdiagnosis. This study reviewed cases with characteristic focal dorsal indentation of the spinal cord, highlighting the importance of accurate diagnosis for treatment planning.