Thoracic paraspinal lesion: question

Abstract

Spinal meningeal cysts are rare lesions and comprise approximately 1–3% of spinal tumors [1–4]. Nabors et al. published a classification for spinal meningeal cysts classifying them into three categories [1]. Type I cysts are extradural meningeal cysts without spinal nerve root fibers. These lesions are further divided into type IA, or extradural meningeal/arachnoid cysts as in this patient, and type IB, or occult sacral meningoceles. Type II extradural meningeal cysts include nerve root fibers and are also known as Tarlov’s perineural cysts or spinal nerve root diverticuli. Spinal intradural meningeal/arachnoid cysts are classified as type III. Tarlov cysts remain one of the most common of these lesions and are often visualized on spinal imaging performed for various indications. Type I cysts have been attributed to arachnoid herniation through a congenital dural defect or congenital diverticula of the dura [1]. Familial tendencies for spinal meningeal cysts and association with other congenital anomalies are known [3]. Continued secretion of cerebrospinal fluid by the arachnoid in a cyst or a ball-valve effect trapping cerebrospinal fluid within the cyst after entry through its pedicle may explain extradural cyst enlargement [2]. Approximately 65% of spinal cysts occur in the thoracic spine [4]. Cysts are most commonly located dorsally and can be associated with ventral compression and thinning of the spinal cord [1]. In each of the 22 cases described in the original article by Nabors et al., patients were symptomatic with pain or neurological deficits [3]. In the present era, however, most of these lesions are actually asymptomatic and are now discovered incidentally on MRI [1]. When present, symptoms vary by level of the cyst;