gms | German Medical Science

Most frequent neoplasms in the region of petrous apex are meningioma and epidermoid. In their slow growth they can penetrate clival region, cerebellopontine angle, middle cranial fossa, and even invade cavernous sinus. In advanced stages it becomes interdisciplinary problem, requiring co-operation of neurosurgeon, ENT or facial surgeon. Petrosal approach is one of the combined accesses to the posterior cranial base. It allows access to lesions located in parasellar region, cavernous sinus, petrous ridge, cerebellopontine angle region or even region of foramen magnum [Ref. 1], [Ref. 2], [Ref. 3]. The patient is operated in supine position with the head fixed in frame. Skin incision extending from the zygoma above the ear up to retromastoid region. Temporal bone mastoid and posterior fossa bony surface of are exposed. Temporo-occipital craniotomy with free osseous flap is performed. During craniotomy the dura in region of transverse and sigmoid sinuses should be carefully dissected. Partial petrosectomy and complete mastoidectomy is performed around the labyrinth using high-speed drill. A sigmoid sinus and superior petrosal sinus are sceletonized and the dura of the posterior fossa anterior to the sigmoid sinus is exposed. During petrosectomy (using diamond drill) the facial canal, semicircular canals and other middle and inner ear structures should be identified and preserved. Intraoperative neurophysiological monitoring should be applied in this procedure. The dura above temporal lobe is opened with special care on the vein of Labbé which should be dissected from cortex and preserved. The dura of the posterior fossa is incised parallel and anteriorly to the sigmoid sinus. Both incisions are connected by ligation (or clipping) and sectioning of the superior petrosal sinus. Tentorium is sectioned along the petrous ridge up to the incisura. Two spatulas are necessary to elevate temporal lobe and retracted cerebellum and sigmoid sinus.

Eleven consecutive patients with tumours of the petroclival region have been operated using petrosal approach in period 1999–2004 at Department of Neurosurgery Medical University of Silesia in Katowice. There were eight petroclival meningiomas (one recurrence after incomplete resection via retrosigmoid approach), and recurrences of one epidermal cyst, one chondromyxoma and one haemangiopericytoma (also after retrosigmoid craniectomy) in our group. The patient’s ages ranged from 19 to 67 years. During operation continuous monitoring of AEP, SEP and EMG from 4^th (oblique inferior muscle) 5^th, (masseter muscle) 6^th (stright lateral muscle), and 7^th (orbicular muscle of eye) cranial nerves was performed using Nicolet Viking IVD unit. In selected cases intraoperative monitoring of cochlear function was also conducted using distortion product otoacoustic emissions (DPOAEs). Details of our methods of multimodal monitoring have been published [Ref. 4], [Ref. 5]. In three cases preoperative embolisation of the feeding vessels was possible (Table 1 [Tab. 1]).

Total resection of the tumor was achieved in 8 cases (78%), subtotal in 3 cases. There was no immediate postoperative mortality, one patient (W.W. in Table 1 [Tab. 1]) died on 10^th day after operation due to pulmonary embolism. She presented very good immediate postoperative neurological condition. In 1 case severe complication - brainstem ischemia with deep haemiparesis appeared. Other details of neurological state before and after procedure are presented in Table 1 [Tab. 1].

One of the main advantages of petrosal approach is fact that tumors supply can be reached and coagulated at the beginning of meningioma extirpation. However embolisation of vascular supply may bee a key for successful meningioma removal. Other advantages of this access are: short distance from cortex to clivus, wide exposure of operating field and cranial nerves (in some cases from III-th nerve even to caudal cranial nerves), possibility of hearing preservation, minimal retraction of brain tissue. Our observations proved opinion of other authors [Ref. 1], [Ref. 2], [Ref. 3] ]. Mortality, extension of tumor removal, complications rate as well as postoperative deterioration of cranial nerves function in our group is comparable to results obtained by other very experienced authors who for management of petroclival lesions employed similar or other approaches [Ref. 6], [Ref. 7], [Ref. 8], [Ref. 9], [Ref. 10].

Petrosal approach provides excellent exposure and access to tumors (especially meningiomas) located in petroclival region, anterior cerebellopontine angle, Meckel's cave region even in cavernous sinus and enabled to successful removal of them with relatively low number of complications.