Symptomatic Tarlov cyst in cervical spine

Description

Perineural cysts known popularly by the eponym Tarlov cysts appear on dorsal nerve roots commonly in the sacral spine.¹ These are a radiological diagnosis with MRI being the gold standard imaging. Most are benign and asymptomatic but occasionally they can be symptomatic. The treatment options for these symptomatic cysts include conservative (oral steroids and non-steroidal anti-inflammatory drugs (NSAIDs)), transforaminal epidural injections and rarely in occasional cases a surgical ablation.^2–4

We report the image of the 45-year-old male patient suffering from radicular symptoms with pain in the lateral side of his left forearm, burning sensation and numbness of his left thumb. There was no prior history of trauma or any chronic problems except that he was a heavy smoker. On examination, muscle strength of both upper extremities was 5/5 with sensory 2/2 except in C6 dermatome with altered sensation. The pain aggravated with tilting the head to an opposite direction. Plain X-ray of the cervical spine was unremarkable and an MRI of the cervical spine revealed a normal sagittal profile but axial cuts showed a perineural cyst on the left on the C5–C6 level (figure 1A,B). The patient received a 2 week’s course of NSAIDs, oral steroids and a soft collar with restriction of his activities, especially extreme stretching of his arm and neck. The patient reported some improvement and at 1 year, there was a satisfactory outcome with over 90% improvement of his symptoms. We did not repeat MRI to see the fate of the exiting perineural cyst.

Figure 1.

Axial T2-weighted image of the cervical spine shows a well-defined oval hyperintense cystic lesion in the left side neural foramen at the C5/6 level (A). Corresponding lesion in the fat-saturated coronal T2-weighted image (B).

Perineural cysts are meningeal dilatation occurring along the nerve roots about the dorsal ganglion. The prevalence is about 4.6% in population but may be actually under-reported. Gossner et al found there may be more common to the tune 14% in their institutional study.⁵ The histopathological study reveals nerve fibres in the wall of these cysts.^{1 4} The cysts are ornamental except occasionally they compress the nerve root to produce sciatica, sacral or buttock pain. The cervical cyst is a rare finding and sparsely described in the literature but they can be picked up on MRI with a signal isointense to cerebrospinal fluid (CSF) and location typically in the vicinity to the dorsal ganglion. The presence of any coexisting pathology is crucial to test the correlation between clinical and radiological findings in a patient with such a cyst.

The literature regarding treatment algorithm of symptomatic Tarlov is lacking due to its rarity. Some authors have found satisfactory outcome with a conservative approach for symptomatic cervical Tarlov cyst using oral steroids or even a transforaminal epidural steroid injection in one case.^{2 3 6} Steroids aim to reduce neural inflammation causing the radicular symptoms, and a follow-up MRI can reveal a shrunken cyst.² Joshi et al had to go for surgical excision in their case of a large Tarlov cyst mimicking a cervical spinal tumour.⁷ The surgery per se has its own technical difficulties and challenges as repair of such small lesions may be associated with complications of nerve root injury, postoperative CSF leak and subsequent persistent neuropathic pain.⁸

The current case is unusual due to its location published in the literature and ‘symptomatic’ with no other associated pathological findings on MRI. The management was conservative as there was minimum neurological affection. Tarlov cyst is an important differential diagnosis and carefully searched in MRI of patients with radicular symptoms rising even from the cervical spine. The aim of the write-up was to sensitise the readers about this rare entity for its more ubiquitous location and differentiation from the spinal tumours.

Learning points.

• Tarlov cysts are incidental finding on MRI that can be missed and both clinicians and radiologist must be aware of it.

• Though asymptomatic, occasionally they can produce compression and reporting is necessary when actually radiologist feel unnecessary.

• Cervical spine is an unusual described location but may actually be as many went unreported.