Intradural spinal arachnoid cyst contributing to sudden paraparesis

INTRODUCTION

Spinal arachnoid cysts are filled with cerebrospinal fluid (CSF). They may be congenital or acquired (e.g., occur after trauma, hemorrhage, infection, or iatrogenic insults). They can be extra- and intra-axial or intramedullary lesions and are maybe communicating or noncommunicating with the CSF space. Symptoms of spinal compression are rare but may include pain, hypesthesia, paresis, and sphincter dysfunction.[5] Here, we report a 37-year-old female with an intradural thoracic arachnoid cyst at the T7 level whose rapid onset of paraparesis was attributed to acute cyst expansion. Following surgical decompression, her symptoms and signs fully resolved.

CASE REPORT

A 37-year-old female presented with the sudden onset of abdominal pain rapidly accompanied by numbness and weakness in both lower extremities. On examination, she was paraparetic (right 3/5 and left 4/5 proximally/distally) and exhibited decreased pin, temperature, vibration, and position perception below the T8 level.

Diagnostic studies

The thoracic magnetic resonance image (MRI) revealed a dorsal intradural extramedullary cyst at the T7 level, compressing, and displacing the cord anteriorly. The T2-weighted image is showed a high-intensity uniform cyst (filled with cerebral spinal) [Figure 1]. The myelogram further demonstrated a near complete block at the T7 level (e.g., intrathecal contrast only slowly passed the T7 level extending cephalad). The thoracic computed tomography myelography confirmed the presence of a uniformly filling arachnoid cyst [Figure 2a-c].

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Figure 1: Initial thoracic magnetic resonance image (T2-WI) (a) Sagittal view – an intradural extramedullary cyst was located at the T7 level dorsal to the spinal cord. (b) Axial view, serial cross-section around T7 – the cyst compressed the spinal cord anteriorly. The high intensity of the cyst on T2-WI is consistent with a cerebrospinal fluid filling.

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Figure 2: (a) Thoracic myelography (A-P image) – the contrast medium was blocked at the T7 level. (b) Thoracic axial computed tomography after myelography at the T7 level – the cyst was filled with contrast medium. (c) Thoracic sagittal computed tomography after myelography – the contrast medium filled both the subarachnoid space and the cyst uniformly.

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DISCUSSION

Spinal arachnoid cysts are rarely symptomatic but occasionally contribute to slowly or occasionally rapidly progressive motor/sensory paraparesis and sphincter disturbance.[1,2] Ventral cysts contribute more to myelopathy/paresis, while dorsal cysts usually contribute to greater sensory disturbances.[6] The median duration of symptoms before diagnosis was 8 months–3.6 years, with radicular pain being present an average of 4.7 months. Alternatively, three studies reported the acute onset of spinal arachnoid cysts.[4,6,7]

Compression by enlarging cysts may contribute to spinal cord dysfunction. The mechanism of growth is typically due to fluid secretion from the cyst wall cell themselves, active transport of water according to osmotic gradient, or a one-way valve allowing fluid movement to the cyst after CSF pressure fluctuations.[1]

Valsalva-like maneuvers during daily activities, such as coughing, straining, standing up, and compressing the abdomen, can make large CSF pressure fluctuation due to distension of the epidural vein influenced by abdominal or thoracic cavity pressure changes.[3] Only this one-way valve with CSF pressure, fluctuation theory could explain acute-onset symptoms.

All instances of intradural extramedullary cysts, including our case, undergoing decompression/cyst removal, resulted in complete recovery.[4,6,7]

CONCLUSIONS

A 37-year-old female with a symptomatic intradural spinal arachnoid cyst at the T7 level presented with the sudden onset of paraparesis. The patient underwent a T6-T8 laminectomy 2 weeks after presentation, and she was asymptomatic by the 4^th postoperative week.