Modified orbitozygomatic and far-lateral approaches adequately expose the midbasilar region and can replace transpetrosal approaches in some cases. These extended approaches can be associated with lower morbidity rates than can transpetrosal approaches. Hypothermic circulatory arrest is critical to clipping large and giant midbasilar artery aneurysms directly when approaches that conserve the temporal bone are used.
The presence of perilymph fistula has been difficult to determine because of the lack of efficient and reliable testing methods. The condition is suspected on the basis of history alone and confirmed by surgery. This paper details a quick, reliable procedure called the ENG fistula test, using impedance bridge for pressure change and electronystagmography to aid the establishment of nystagmus and dizziness. To evaluate this procedure, a combination of tests were performed, including Valsalva maneuver, tragal compression, and pneumatic otoscopy, which were previously considered helpful in the diagnosis of fistula. Of them, Valsalva maneuver and tragal compression proved inconclusive; pneumatic otoscopy proved to be helpful. In comparison, however, the ENG fistula test proved most valuable, with results surgically confirmed in 90.8% of cases in this series. This study involved 74 patients whose primary complaint was dizziness. Only some patients simultaneously experienced hearing lows. Included are 5 patients whose positive ENG fistula test results and 15 whose negative test results were confirmed by surgery. Selected case histories are presented.
The combination of the subtemporal and posterior fossa approaches has been used for many years to gain exposure of lesions in the clivus or medial petrous region. We have divided this approach, popularized by Malis, into three variations with progressively greater petrous bone resection to increase exposure of the clivus and medial petrous region. The approach has been divided into petrous bone resection with preservation of hearing (retrolabyrinthine), greater petrous bone resection with sacrifice of hearing (translabyrinthine), and, finally, maximum petrous drilling with sacrifice of hearing along with transposition of the facial nerve (transcochlear). By combining the skills of a neurosurgeon and a neuro-otologist, the operative exposure can be maximized. We present our experience with 30 cases of the combined approach, its variations, and its indications. METHODSThe surgical team consists of a neurosurgeon versed in skull base surgery and a neuro-otologist versed in all transmastoid-transcochlear procedures. The patient is positioned supine on the operating table with the head turned parallel to the floor and fixed to the operating table with the Mayfield headholder with appropriate shoulder support. The incision begins at the level of the zygoma 1 cm anterior to the ear and is continued in a gentle curving fashion around the ear to end just below the mastoid tip (Fig. 1). The incision can be modified by moving the posterior limb of the incision further posterior if greater exposure is necessary. The lateral side of the skull is exposed by retracting the scalp inferiorly with fish hooks. This maneuver exposes the zygoma, lateral temporal bone, external auditory meatus, and mastoid region. If more anterior exposure is required, the external auditory canal is transected and oversewn in two layers.The neuro-otologist performs the temporal bone approach using the Midas Rex (Midas Rex, Fort Worth, TX) high-speed drill system for the mastoidectomy portion and then changing to the Osteon (Hall Surgical, Santa Barbara, CA) system for more detailed bone removal under the operating microscope. Suction irrigation is used throughout. If hearing is to be preserved, an extended Skull
The authors report the unusual presentation of an intracranial extension of synovial chondromatosis of the temporomandibular joint. The patient presented with a peripheral facial nerve paralysis and anacusis. Computerized tomography revealed the lesion, but fine-needle biopsy was inconclusive. Craniotomy with removal of the tumor was performed, and pathological studies confirmed the diagnosis. The facial nerve dysfunction was thought to be secondary to direct neural compression.
We believe that our initial experience establishes the fact that ABRs can be routinely and reliably performed in an operating room environment. There was no added risk to the patient, and operative delays were minimal. We did note transient fluctuation in latency values up to 1.5 msec. These changes would revert to baseline levels within five to ten minutes. Changes noted during drilling were probably related to the random noise produced. Case 3 was worrisome in that hearing was lost after maintenance of the ABRs during the surgical procedure. Evidently the vestibule was damaged, and a labyrinthitis caused the hearing loss. We feel that this procedure will be most useful in those situations in which the cochlear nerve and blood vessels are at risk. Such procedures as acoustic tumor removal with attempts to preserve hearing, vestibular nerve sections, and facial nerve problems in the IAC should be routinely monitored. Further experience will, of course, be most helpful in explaining and recognizing these changes.
Pathological entities such as schwannomas and meningiomas can appear on imaging studies as contrast-enhancing masses in the cerebellopontine angle (CPA) cistern. 3 Focally enhancing pathological entities of vascular origin in the CPA include ectatic vessels; aneurysms, especially those of the anterior inferior cerebellar artery; and "high-riding" jugular bulbs with dehiscent overlying bone. 3 Draining veins of arteriovenous malformations or arteriovenous fistulae can also demonstrate contrast enhancement. 1,2 We present a case of superior petrosal vein varicosity that presented as an enhancing CPA lesion. This appearance of a normal variant has not been reported previously. This 56-year-old woman with the complaint of recurrent left-sided tinnitus underwent magnetic resonance imaging, which revealed an enhancing lesion at the level of the left internal acoustic meatus (Fig. 1). The differential diagnosis included an eighth-nerve schwannoma, meningioma, aneurysm, or vascular malformation. The patient underwent four-vessel cerebral angiography, which revealed only an isolated segmental ectasia of the superior petrosal vein with no other associated vascular anomalies (Fig. 2). To our knowledge, there have been no previous reports of superior petrosal vein ectasia presenting as an enhancing lesion of the CPA. This entity should be considered to be an extremely rare cause of enhancement in the CPA cistern. When indicated, cerebral angiography will help establish the diagnosis and avoid unnecessary exploratory surgery or stereotactic radiotherapy.
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