Is scan‐negative cauda equina syndrome a functional neurological disorder? A pilot study

BACKGROUND: Cauda equina syndrome (CES) is a neurosurgical emergency which warrants a lumbar MRI. Many patients with suggestive symptoms of CES have no radiological correlate. A functional (non-organic) aetiology has been proposed in some, but currently little is known about this patient group and their clinical outcomes. METHODS: At a tertiary referral centre, 155 adult patients underwent urgent lumbar MRI for suspected CES in one year from December 2014. Data regarding clinical symptoms and follow-up were obtained from records. Patients were divided into CES (n=25), radiculopathy (n=68) and scan-negative (SN) groups (n=62) from scans. Up to 3 years post-discharge, postal questionnaires were sent to patients with Owestry Disability Index, Pain Catastrophising score, PHQ-9, GAD-7, PHQ-15 and WSAS measures. RESULTS: No clinical symptoms were found to differentiate CES from SN patients. Functional co-morbidities were significantly more common in SN patients but mental health diagnosis frequency did not differ. Follow-up was variable with no consistent referral pathways, particularly for the SN group. 33% (n=47) responded to postal questionnaires; high levels of pain, symptom chronicity and disability were ubiquitous but self-reported mental health diagnoses and PHQ-15 were higher for SN patients. CONCLUSIONS: Conflicting data suggests further research is needed to investigate the prevalence of mental illness and somatic symptoms in SN cases. SN patients have higher rates of co-morbid functional disorders and inconsistent referral pathways. Self-report measures indicate impaired quality of life across all groups. The low response rate limits the generalisability of findings but neuropsychiatric assessment and care pathway optimisation should be considered.