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

Cauda equina syndrome (CES) is a neurosurgical emergency which warrants lumbar magnetic resonance imaging (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.

At a tertiary referral centre, 155 adult patients underwent urgent lumbar MRI for suspected CES in 1 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 Oswestry Disability Index, Pain Catastrophizing score, Patient Health Questionnaire (PHQ) 9, Generalized Anxiety Disorder (GAD) 7, PHQ 15 and Work and Social Adjustment Scale measures.

No clinical symptoms were found to differentiate CES from SN patients. Functional comorbidities 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 the 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.

Conflicting data suggest further research is needed to investigate the prevalence of mental illness and somatic symptoms in SN cases. SN patients have higher rates of comorbid functional disorders and inconsistent referral pathways. Self-report measures indicate impaired quality of life across all groups. The low response rate limits the generalizability of findings but neuropsychiatric assessment and care pathway optimization should be considered.