Extended Middle Fossa Approach to Lateralized Pontine Cavernomas in Children

Objective Treatment of hemorrhagic cavernous malformations within the lateral pontine region demands meticulous surgical planning and execution to maximize resection while minimizing morbidity. We report a single-institution's experience using the extended middle fossa rhomboid approach for the safe resection of hemorrhagic cavernomas involving the lateral pons.

Methods A retrospective chart review was used to identify and review the surgical outcomes of patients who underwent an extended middle fossa rhomboid approach for the resection of hemorrhagic cavernomas involving the lateral pons during a 10-year period at Rady Children's Hospital of San Diego. Surgical landmarks for this extradural approach were based on the Fukushima dual-fan model, which defines the rhomboid based on the following anatomic structures: (1) the junction of the greater superficial petrosal nerve (GSPN) and mandibular branch of the trigeminal nerve (V3); (2) the lateral edge of the porous trigeminus; (3) the intersection of the petrous ridge and arcuate eminence (AE); and (4) the intersection of the GSPN, geniculate ganglion, and AE. The boundaries of maximal bony removal for this approach are the clivus inferiorly below the inferior petrosal sinus; unroofing of the internal auditory canal posteriorly; skeletonizing the geniculate ganglion, GSPN, and internal carotid artery laterally; and drilling under the Gasserian ganglion anteriorly. This extra-dural petrosectomy allowed for an approach to all lesions from an area posterolateral to the basilar artery near its junction with CN VI, superior to the anterior inferior cerebellar artery (AICA), and lateral to the origin of CN V. Retraction of V3 during this approach allowed avoidance of the region involving CN IV and the superior cerebellar artery (SCA).

Results Eight pediatric patients (5 girls and 3 boys, mean age of 13.2 ± 4.6 years) with hemorrhagic cavernomas involving the lateral pons were treated utilizing the above surgical approach. Seven cavernomas were completely resected. In the eighth patient, a second peripheral lesion was not resected with the primary lesion. One patient had a transient CN VI palsy, and two patients had transient trigeminal hypoesthesia/dysesthesia. One patient experienced a cerebrospinal fluid leak that was successfully treated by oversewing the wound.

Conclusion The extended middle fossa approach can be used for resection of lateral pontine hemorrhagic cavernomas with minimal morbidity in the pediatric population.