By Michael Rubin, MD
Professor of Clinical Neurology, Weill Cornell Medical College
SYNOPSIS: Tarlov cysts (root sleeve cysts) are common incidental findings on magnetic resonance imaging of the lumbosacral spine. However, they rarely are correlated with electrophysiological findings or clinical symptoms. Extreme care and caution should be undertaken before recommending surgical intervention for these common imaging abnormalities.
SOURCE: Hentzen C, Cabrilo I, Malladi P, et al. Sacral Tarlov cysts: Neurophysiology abnormalities and correlation with pelvic sensory and visceral symptoms. Eur J Neurol 2023;30:2838-2848.
Among the less common conditions that may be associated with radiculopathy are root sleeve or perineural cysts (Tarlov cysts; TCs), most often present on the S2 or S3 nerve root. They are found more frequently in women and with increasing age, with an estimated prevalence of 4%, often found incidentally on lumbosacral magnetic resonance imaging (MRI) performed for various medical conditions. Most TCs are asymptomatic, but when localizing to the patient’s complaints, the question arises as to whether they are causative and, if so, should they be drained or otherwise treated. In this study, sacral TCs and their relation to pain, sphincteric or sexual symptomatology, and pelvic neurophysiology were examined.
Between January 2017 and July 2021, patients with suspected symptomatic TC, referred for uro-neurologic assessment at the National Hospital for Neurology and Neurosurgery, Queen Square, London, UK, underwent cross-sectional neurologic and pelvic organ evaluation. Bladder, bowel, sensory, and sexual symptoms were evaluated using the Urinary Symptom Profile, the Constipation Scoring System, and the Arizona Sexual Experiences Scale, while pelvic neurologic examination encompassed sacral reflexes and motor function of the external anal sphincter, with evaluation of pelvic dermatomal sensation using a Neurotip and Von Frey hairs. Pelvic neurophysiologic study included pudendal and S2 and S3 dermatomal sensory evoked potentials (SEPs) and external anal sphincter electromyography (EMG).
Urodynamic assessment was performed only in patients reporting significant lower urinary tract symptoms or significant voiding dysfunction and comprised noninvasive uroflowmetry and measurement of post-void residual volumes, with invasive multichannel urodynamic studies, including filling cystometry and pressure-flow studies following International Continence Society Good Urodynamic Practices. Lumbosacral MRIs, acquired closest to the date of the neurophysiology investigation, were reviewed by the same observer. Sacral cystic lesions other than TC were excluded. Statistical analysis comprised Chi square testing, and Fisher and analysis of variance (ANOVA) tests, with significance set at P < 0.05.
Among 73 patients reviewed, only four were male and hence excluded, both because of their small number as well as because of technical difficulties performing pudendal SEPs. Unrelated pelvic pathology that interfered with test interpretation excluded four additional patients. Among the 65 remaining women, with a mean age of 51.2 years, pain was the most common symptom (92%), followed by urinary (91%), bowel (71%), and sexual symptoms (80%). Multiple or bilateral cysts were seen in 86%, and 57% had abnormal pelvic neurophysiology indicative of sacral root dysfunction, including 42% with abnormal dermatomal SEPs, 26% with abnormal pudendal SEPs, and 16% with abnormal external anal sphincter EMG.
However, neurophysiology abnormalities correlated neither with MRI findings nor urodynamic findings, nor with reported bowel symptoms or sexual dysfunction. Injury to the sacral somatic innervation is associated with TC in most patients with presumed symptomatic cysts, but urinary incontinence is unlikely to be related to such TC-induced nerve damage.
COMMENTARY
Up to 22% of TCs appear to compress the enclosed nerve fibers and, when associated with back pain, limb weakness, or paresthesiae, and sphincteric or sexual dysfunction, offer enticing targets for therapeutic intervention.
What might be offered? Interventional options include cyst aspiration with injection of fibrin glue, cyst fenestration, and nerve root imbrication (surgical repair of nerve roots). Among 95 patients managed interventionally over a 15-year period at the Department of Neurosurgery, Johns Hopkins University School of Medicine in Baltimore, computed tomography-guided cyst aspiration with fibrin glue injection was performed in 71 patients, cyst aspiration alone in 17 patients, blood patching in five patients, with two patients undergoing more than one of these procedures. Improvement was seen in 66%, with none of the procedures being statistically superior. Cyst aspiration may be looked at as a diagnostic tool to determine if a TC is responsible for symptoms, at which point neurosurgical intervention with cyst fenestration and nerve root imbrication may be offered.1
REFERENCE
- Tracz J, Judy BF, Jiang KJ, et al. Interventional approaches to symptomatic Tarlov cysts: A 15-year institutional experience. J Neurointerv Surg 2023; Jul 4. doi: 10.1136/jnis-2023-020564. [Online ahead of print].
