Posttraumatic Arachnoid Cyst in the Thoracic Spine with Medullary Compression: Case Report

Abstract

Arachnoid cysts are rare; they can occur at all levels of the dural sac, and can have a congenital, traumatic, iatrogenic or inflammatory origin. In the present article, we report a patient presenting a compressive thoracic myelopathy due to an unusual intradural arachnoid cyst with posttraumatic manifestation and its resolution, in addition to a literature review on the subject. These cysts mainly occur at the thoracic spine, followed by the lumbar, lumbosacral and thoracolumbar spines. Traumatic cysts are caused by an injury to the inner dural layer. These lesions produce neurological deficits through a mass effect on the spinal cord. Concomitant compressive myelopathy is even rarer. In case of myelopathy, cyst resection or drainage is the treatment of choice, and it must be performed immediately. Although rare, arachnoid cysts can be a complication of spine fractures; as such, orthopedists and neurosurgeons, who commonly see these injuries, must be prepared for this unusual situation.

Keywords: arachnoid cysts; spinal cord compression; spinal cord injuries.

Fig. 1

Sagittal T2-weighted magnetic resonance imaging showing an old fracture at the T10 vertebral body; space widening between the T9-T10 spinous processes, suggesting chronic ligament rupture; alteration of the spinal-cord signal at the T9, T10 and T11 levels, consistent with myelomalacia; posterior adhesion of the spinal cord at the T7-T9 level, and anterior adhesion at the T9-T12 level, associated with adhesive arachnoiditis and an arachnoid cyst at these levels. The white arrows show the boundaries of the cyst and posterior spinal adherence.

Fig. 2

Laminectomy and costotransversectomy (white arrows) after the insertion of the pedicle screws at the T8 and T11 levels to approach the arachnoid cyst and perform the subsequent stabilization.

Fig. 3

Microscope image showing durotomy and cyst drainage at the T9 and T10 levels.

Fig. 4

Repair of arachnoid cyst using primary, 5-0 non-absorbable nylon suture. The arrows highlight the edge of the durotomy to approach the cyst.

Fig. 5

Posterolateral and lateral radiographs of the thoracic spine at the end of the procedure, showing adequate position and alignment of the pedicle screws.

Fig. 1

Ressonância magnética, cortes sagitais, ponderada em T2, evidenciou: fratura antiga do corpo vertebral de T10; alargamento do espaço entre os processos espinhosos de T9 e T10, sugerindo rotura ligamentar crônica; alteração do sinal da medula espinhal no nível de T9, T10 e T11, compatível com mielomalácia; e medula espinhal aderida posteriormente no nível de T7 a T9 e anteriormente de T9 a T12, associada a aracnoidite adesiva e cisto aracnóide nos níveis descritos. Nos cortes axiais, no nível de T9, observamos a medula posteriorizada no canal vertebral e o cisto caracterizado pelo hipersinal. As setas em branco demonstram os limites do cisto e a aderência medular posterior.

Fig. 2

Laminectomia e costotransversectomia (setas em branco) após a inserção de parafusos pediculares nos níveis de T8 e T11 para acesso ao cisto aracnóide e posterior estabilização.

Fig. 3

Imagem do microscópio demonstrando a durotomia e a drenagem do cisto nos níveis T9 e T10.

Fig. 4

Reparo do cisto aracnóide por meio de sutura primária com fios não absorvíveis de náilon 5-0. Borda da durotomia de acesso ao cisto em destaque nas setas.

Fig. 5

Radiografias da coluna torácica, nas incidências posterolateral e de perfil, ao final do procedimento, demonstrando posicionamento e alinhamento adequados dos parafusos pediculares.