Keyhole Retrosigmoid Craniotomy for Lateral Pontine Cavernous Malformation.

With improvements in anesthesia, monitoring, and peroperative care, the surgical removal of intrinsic brainstem pathology has become a possibility.1 Although surgical removal of deep-seated lesions continues to have significant morbidity, at least temporarily, associated with it, removal of exophytic lesions can be accomplished with little disability for the patient. The key to a good outcome, when removing cerebral cavernous malformation, is preservation of adjacent neurovascular bundles, use of sharp dissection over blunt pulling, judicious use of cautery in and around the brainstem, and preservation of the developmental venous anomaly, when present. The authors present a case of a lateral pontine cerebral cavernous malformation that was exophytic at the lateral and peritrigeminal safe entry zones.2 Neuromonitoring was used an adjunct to ensure safety of the procedure. The lesion is accessed using a keyhole retrosigmoid craniotomy (Video 1). We do not routinely use lumbar drains for these procedures as careful arachnoid dissection can result in adequate cerebrospinal fluid release. The window of access to this area is between CN 5 and the CN 7/8 complex. The arachnoid over the nerves is preserved, but the layer between the nerves is exposed to gain access to the lateral pons. The lesion is sharply dissected from the lateral pons, taking care to save the developmental venous anomaly, from which this lesion arises.

Symptomatic Outcome after Bone-only Suboccipital Decompression in Adult Patients with Chiari Type I Malformations in the Absence of Hydromyelia or Hydrocephalus.

Background Type I Chiari malformation presents without an associated hydromyelia in 30 to 70% of cases, yet there is no agreement regarding the optimal surgical treatment for these patients. We review our experience for treating symptomatic adult type I Chiari malformation without hydromyelia using a suboccipital bone decompression of the hindbrain and no duraplasty in 12 adult patients. Outcome was measured according to the Chicago Chiari Outcome Scale (CCOS). Results Nine of 12 patients were female; average age at surgery was 34.4 years (range: 17-67 years). Average duration of symptoms prior to surgery was 9.6 years (2 months-29 years). The most common symptom was head and/or neck pain (11/12 patients). All patients additionally presented with at least one non-pain symptom. Mean degree of tonsillar herniation on magnetic resonance imaging was 6.8 mm (range: 5-12 mm) below McRae's line. Operative time was on average 68 minutes (range: 47-120 minutes). No surgical complications were noted in any patient. Length of hospital stay was 2 days (1 overnight) for all patients. Mean follow-up was 167 weeks (range: 13-378 weeks). CCOS for all patients on average was 14.50 (range: 12-16). Pain symptoms underwent improvement (7/11 [63.6%]) or complete resolution (4/11 [36.4%]) in all affected patients. A shorter duration of preoperative symptoms significantly correlated with a better CCOS (p = 0.03). Degree of tonsillar herniation had no significant effect on CCOS (p = 0.67). Of non-pain symptoms, paresthesias/dysesthesias and visual symptoms improved or resolved completely in all affected patients. No patient experienced a worsening of either pain or non-pain symptoms. Conclusion In the subset of adult patients with a type I Chiari malformation and no associated hydromyelia, a craniectomy without an additional opening of the dura may achieve good overall results according to the CCOS.