gms | German Medical Science

Objective: Suboccipital decompression is considered the treatment of choice for Chiari I malformation. Several studies have shown the improvement of neurophysiological parameters during decompressive surgery. However, the role of intraoperative neuromonitoring in preventing neurologic deterioration is still controversial.

Method: 39 patients (25 female, age 41.1±14.5 [mean±SD]) underwent suboccipital decompression for treatment of symptomatic Chiari I malformation. In all patients a continuous intraoperative monitoring with somatosensory-evoked potentials of the median nerve (M-SEP) and the posterior tibial nerve (T-SEP) and motor-evoked potential to the hand (H-MEP) and foot (F-MEP) was applied, alone or in combination. The M-SEP N20, T-SEP P40, H-MEP and F-MEP amplitudes and latencies were recorded at the beginning of the surgery (baseline) and after dura closure.

Results: There was no significant change of M-SEP N20, T-SEP P40 or H-MEP and F-MEP amplitudes or latencies comparing baseline to final measurements (p>0.05, Student’s t-test). The average time between both recordings was 125±48 min (mean±SD). Postoperatively, none of the patients showed new neurological deficits. During the mean follow-up period of 22.4±20.3 (mean±SD) months, 92.6% of the symptoms showed an improved or stable status. Three patients (8.1%) presented a relapse of the symptoms after 25.7±7.6 (mean±SD) months, only one patient (2.5%) needed a secondary decompression after 24 months.

Conclusions: Intraoperative neuromonitoring is not a prerequisite for a safe suboccipital decompression in primary treatment of Chiari I malformation.