Dorsal thoracic arachnoid web as a rare cause of syringomyelia

This is an unauthorised machine translation into English made using the DeepL Translate Pro translator. The editors do not guarantee that the content of the article corresponds fully to the original language version.

Dear Editor,

The dorsal thoracic arachnoid web is one of the rare causes of intradural extramedullary compression of the spinal cord [1]. It is a thickened band of arachnoid membrane that causes local pressure on the spinal cord [2]. These bands are sometimes considered remnants of an arachnoid cyst that arise from its collapse or spontaneous evacuation [2]. Most commonly, it compresses the thoracic spinal cord on its posterior side (95%), less frequently on the anterior side (2.5%), or completely encircles it (2.5%) [3].

Possible causes include post-infectious etiologies, trauma, or previous surgery, with the latter two being identified in the medical history of 16% of patients [2,3]. It occurs more frequently in men with a median age of 52 years [3]. Among the clinical symptoms, which are not very specific, the most common are back pain with weakness of the lower extremities. This may sometimes be associated with sphincter dysfunction [4].

MRI is the preferred imaging modality. A typical finding here is the so-called scalpel sign, characterized by a localized depression most commonly on the dorsal side of the upper thoracic spinal cord [1], and because the arachnoid bands themselves are difficult to visualize, the scalpel sign is one of the indicators of the need for surgical intervention [1]. Another relatively common finding is syringomyelia, which occurs in approximately 67% of cases [3].

In the case of a confirmed diagnosis of dorsal thoracic arachnoid web, combined with clinical symptoms, surgical intervention is indicated; this most commonly involves laminectomy with intradural incision of the arachnoid web. Other surgical approaches, such as hemilaminectomy or endoscopic surgery, are less common [5]. The effectiveness of the surgical procedure and improvement in clinical symptoms are reported by 79–91% of patients [3,5].

In this paper, we would like to present the case of a patient who was evaluated for paresthesia in the upper extremities and chest, as well as thermal dysesthesia in the left upper extremity. The medical history revealed no history of trauma, neurological infection, or thoracic spine surgery. Objectively, the patient had no neurological deficit. An MRI was performed, which revealed syringomyelia extending from the second thoracic to the third cervical vertebra. On follow-up MRI examinations, the syringomyelia had progressed to the level of the second cervical vertebra (Fig. 1A). Based on the finding of a scalpel sign in a typical location, the radiologist suspected a dorsal thoracic arachnoid web. An electromyographic examination was subsequently performed, which confirmed prolonged central motor and sensory conduction.

After consultation with the patient, a decision was made to proceed with surgery. A left-sided hemilaminectomy was performed. During the operation, a longitudinal thickened band of arachnoid tissue was confirmed at the level of the upper thoracic spine, causing spinal cord compression (Fig. 2). After resection, perioperative ultrasound confirmed adequate spinal cord decompression and partial regression of the syringomyelic cavity.

Postoperatively, the patient reported improvement in symptoms. No objective neurological deficit was present. The course of hospitalization was entirely uneventful. An MRI was also performed, confirming regression of the syringomyelic cavity and adequate spinal cord decompression. On the third postoperative day, the patient was discharged for home care.

At the clinical follow-up 3 months after surgery, the patient reported improved sensation in the left upper limb; a sensation of stiffness in the legs persisted, but there were no limitations in walking or daily activities. The neurological findings were stable. A follow-up MRI of the thoracic spine showed a persistent favorable effect of the surgery (Fig. 1B).

Conflict of Interest

The authors declare that they have no conflict of interest in connection with the subject of the study.