An interesting case of primary spinal arachnoiditis.

Spinal arachnoiditis describes inflammation of the meninges, subarachnoid space and, in most cases, also involve the pial layer. The vast majority of cases described are secondary and are preceded by a known event, for example,. trauma, infections or irritative substances. Here, we present the case of primary spinal arachnoiditis. A 35-year-old lady was referred to the neurosurgical services in Dublin, Ireland with a 15-month history of progressive, right lower limb weakness. Magnetic resonance imaging revealed cystic distortion of the lumbar spinal canal extending up to the conus. Initially, an L2-L4 laminectomy was performed revealing thickened and adherent arachnoid with a large cyst in the spinal canal. Four months after initial operation, the patient represented with bilateral lower limb weakness and loss of detrusor function. Repeat magnetic resonance imaging was performed, which showed the development of a syrinx in the patient's thoracic spine. We then performed a T9-T10 laminectomy, midline myelotomy and insertion of a syringe-arachnoid shunt. Post-operative imaging showed resolution of the syrinx and a vast improvement in lower limb power. The patient also regained bladder control. In conclusion, spinal arachnoiditis is a clearly defined pathological and radiological entity with a highly variable clinical presentation. It is exceedingly difficult to treat as there is no recognised treatment currently, with most interventions aimed at symptomatic relief.