Subdural hygroma after spontaneous rupture of an arachnoid cyst in a pediatric patient: A case report

Abstract

Arachnoid cysts are benign masses that represent a relatively small percentage of intracranial lesions. Spontaneous rupture of an arachnoid cyst resulting in a subdural hygroma is a very rare event. We report a case of a pediatric patient with a history of an arachnoid cyst and chronic headaches presenting with bilateral papilledema, worsening headaches, and no history of head trauma. Magnetic resonance imaging of the brain revealed an extra-axial cystic lesion in the right middle cranial fossa, similar to an arachnoid cyst seen on previous imaging. A new right subdural collection similar to the cerebral spinal fluid signal causing mass effect on brain parenchyma was determined to represent a subdural hygroma. Craniotomy was performed to evacuate the subdural hygroma as well as cyst fenestration. We report this case to emphasize the importance of considering spontaneous rupture of an arachnoid cyst as a differential diagnosis despite absence of head trauma.

Keywords: Arachnoid cyst; Papilledema; Spontaneous rupture; Subdural hygroma.

Fig. 1

(a, b): Axial CT images at 8 months of age. An arachnoid cyst is seen along the right anterior temporal lobe (black arrow). The sulci, fissures, and cisterna are unremarkable. The ventricular system demonstrates no dilatation, distortion, or displacement. There is no displacement of the midline structures. No subdural collections are present in this study.

Fig. 2

(a-c): Axial (a) T2 MR image of an extra-axial cystic lesion in 11-year-old, in the right middle cranial fossa following CSF signal (black arrow). Axial (b) T2 MR image of the subdural hygroma measuring 10 mm in maximal thickness seen along the entire right cerebral convexity (red arrows) causing mass on the underlying brain parenchyma and causing approximately 7-mm leftward midline shift. Coronal (c) T2 MR image showing communication between the right arachnoid cyst and the right cerebral convexity subdural hygroma (yellow arrow). (Color version of figure is available online.)