Craniocervical decompression in patients with mucopolysaccharidosis VI: development of a scoring system to determine indication and outcome of surgery.

OBJECTIVE: To analyse diagnostic value of somato-sensory evoked potentials (SEP), magnetic resonance imaging (MRI), and clinical neurological examination in the decision for decompression surgery in mucopolysaccharidosis (MPS) VI patients with craniocervical cord compression (CCJ).
METHODS: We retrospectively analysed neurological examination, SEP of the median nerve and MRI outcomes from 31 MPS VI patients. Individual scores for each test (based on severity of findings) and a sum of scores of all three procedures (CCJ score) were evaluated for their potential to measure the need for and improvement after surgery. Differences between rapidly and slowly progressive patients were also evaluated.
RESULTS: Fourteen patients (45 %) aged 4-34 years underwent decompression surgery. Median age at first operation was lower in rapidly than in slowly progressive patients (12 vs. 24 years; P = 0.008). Neurological and SEP findings but not MRI results differed significantly between non-operated and operated patients (P < 0.001, P = 0.003 and P = 0.08, respectively). A significant relationship was found between MRI and clinical neurological examination (P < 0.001) and between SEP and clinical neurological examination (P = 0.01) but not between MRI and SEP (P = 0.06). The CCJ score discriminated between operated and non-operated patients (4-9 points vs. 0-3 points; P < 0.001) and decreased in 61.5 % of patients after surgery.
CONCLUSIONS: CCJ is common in rapidly and slowly progressive MPS VI patients. The CCJ score is an objective and transparent tool for assessing pathology of the CCJ, the need for surgery, and improvement after surgery.