Surgical Treatment of Idiopathic Syringomyelia on the Basis of Intramedullary Pulse Pressure Theory: A Report of Nine Cases with Clinical and Radiological Outcomes

Background: The intramedullary pulse pressure theory would provide an explanation of the pathophysiology of idiopathic syringomyelia i.e. Syringomyelia develops where the systolic CSF passes through a regional narrowing in the subarachnoid space which leads to increase in CSF velocity and, according to the Bernoulli theorem, decrease in CSF pressure that would cause a suction effect (Venturi effect) on the spinal cord that distends the cord causing syrinx formation. Objectives: The aim of this study is to describe the clinical and radiological outcomes of surgical management of idiopathic syringomyelia by decompressive laminectomy and syringosubarachnoid shunt on the basis of intramedullary pulse pressure theory. Patients and Methods: This prospective case series study was conducted on nine patients with idiopathic syringomyelia who met our inclusion and exclusion criteria. All the patients were treated by decompressive laminctomy and syringosubarachnoid shunt. Clinical results were evaluated by using the criteria of Japanese Orthopaedic Association Scoring System for Cervical Myelopathy (JOA score). All the patients had preoperative magnetic resonance imaging (MRI) and postoperative MRI two weeks after surgery then every six months in the first year then every year. Radiological results were determined by measuring transverse diameter of the syrinx (TDS) / transverse diameter of the spinal cord (TDSC) percent from axial MRI at the maximum syrinx transverse diameter. Results: The mean age of patients at time of surgery was 32 ±9.79 STD years. 55.6 % of patients were males and 44.4 % were females. The mean duration of symptoms was 54.7 ±25.00 STD months. All patients (100%) had spinothalamic sensory disturbance at time of surgery, 3 patients (33.3%) had posterior column disturbance, 2 patients (22.2%) had dissociative sensory loss, 5 patients (55.6%) had pain in upper limbs, 7 patients (77.8%) had flaccid weakness in upper limbs, 6 patients (66.7%) had spastic weakness in lower limbs and 2 patients (22.2%) had sphincteric disturbance. At the end of follow up (mean 42.4 ±12.12 STD months) the mean JOA score of the patients showed improvement from 8.2 ±2.53 STD before surgery to 14.4 ±1.42 STD and the mean recovery rate was 72.7 (±10.74 STD) %. Also the mean TDS / TDSC percent was reduced from 84 ±7.14 STD % before surgery to 21.1±3.58 STD %. Apart from transient posterior column manifestations, no complication related to surgery was present. Conclusion: The intramedullary pulse pressure theory could explain the pathophysiology of idiopathic syringomyelia. Patients with idiopathic syringomyelia and progressive neurological deterioration could be treated by decompressive laminectomy, to increase the cross-sectional area of the subarachnoid space and stop further propagation of the syrinx, and syringosubarachnoid shunt, to relieve any residual increased pressure within the syrinx for better chance of neurological improvement.