Cranial-Base Surgery for Drug Delivery via Mastoid Cavity: A Novel Procedure for Vestibular/Auditory Syndromes

Objective: The remarkable and rapid evolution of cranial-base surgery has yet to extend complete care for diseases of the vestibulocochlear complex residing deep to the mastoid process of the temporal bone. Studies have shown that the two separate neural end-organs of the vestibulocochlear apparatus share contiguous fluid compartments and often a related/common pathology. Such diseases are oftentimes poorly defined and incompletely understood. Treatment failures are common, and current methods in managing these conditions must be reconsidered. Here, we offer a novel approach for managing such pathologies via a transmastoid cranial-base surgical procedure with evidence of anatomic safety and efficacy. Design: A cadaveric surgical study to assess the anatomic feasibility of implementing a safe and effective drug delivery apparatus via a transmastoid approach to the vestibulocochlear complex. Methods: A total of six transmastoid ab-externo surgical approaches were performed in three cadaver specimens to expose the lateral semicircular canals. Landmarks for safe progress and accuracy were established. A unique technique for a “guarded microcanalostomy” of the lateral semicircular canal wall was developed to permit access to the perilymph space for drug delivery via a catheter supplied by a neurosurgical micropump. This micropump was secured into the adjacent mastoid bone cavity. Results: Satisfactory exposure of the lateral semicircular canals, with proper placement of the pumps and the catheters which were secured to the canals by microcanalostomy, was achieved. The catheter and micropump maintained positional integrity after the specimens were subject to directional, rotational, and contact forces. Conclusion: We offer a novel, cranial-base surgical procedure for drug delivery via a transmastoid delivery system, using an implanted micropump and catheter, to the fluids of the vestibulocochlear complex. Access to this region and to these neural end organs has been limited because of fear of endangering hearing and balance functions and disrupting vital anatomic structures. This surgery will permit effective treatment of multiple sensorineural syndromes of both the auditory and the vestibular systems whether isolated or combined. Applications can include treatment for Ménière disease but also other causes of sudden sensorineural hearing loss and related vestibulocochlear dysfunction. Additional work and confirmation is required.