Surgical Approaches to the Petrous Apex: Distances and Relations with Cranial Morphology

Different pathologies may be located at the petrous apex. The primary surgical approaches used to remove such lesions are the pterional, subtemporal, presigmoid, and retrosigmoid. Each has advantages and disadvantages, and the distance to the petrous apex varies with the approach. Anatomical variations in cranial morphology may interfere with these distances. Dolichocephalic skulls have a longer anteroposterior axis than brachycephalic ones.

Three hundred computed tomographic scans and 65 dry human skulls were analyzed to determine if cranial morphology could indicate the shortest distance to the petrous apex. The distance between the external cortical table of the skull and the petrous apex in each surgical approach was measured. The lengths of the anteroposterior axis (L) and the widths of the lateral axis (W) were measured to determine the cranial index (W/L × 100).

This distance was longest in skulls with a high cranial index (brachycephalic) independent of the approach used. Statistical analysis showed that the distance to the previous apex was longest in the retrosigmoid approach and shortest in the pterional approach in all kinds of skulls. Brachycephalic skulls lose this ellipsoidal shape and the anterior laterolateral diameter is smaller than the posterior laterolateral diameter. Consequently, the distance from the cortical skull table to the petrous apex is shorter in brachycephalic skulls using all surgical approaches described in this article.

Petrous apex - surgical approaches - cranial morphology

REFERENCES

• 1 O'Rahilly R, Crânio e Osso Hióide. In: Gardner E, Gray DJ, O'Rahilly R Anatomia 4th ed. Rio de Janeiro; Guanabara-Koogan 1988: 541-570
• 2 Ramina R, Maniglia J, Barrionuevo C E. Surgical excision of petrous apex lesions. In: Sekhar LN, Janecka IP Surgical excision of petrous apex lesions. New York; Raven 1993: 291-305
• 3 Gianoli G J, Amedee R G. Hearing results in surgery for primary petrous apex lesions.  Otolaryngol Head Neck Surg. 1994;  111 250-257
• 3a Morrison A W, King T T. Experiences with the translabyrinthine transtentorial approach to the cerebellopontine angle. Technical note.  Neurosurgery. 1973;  38 382-390
• 4 Pereira C B, Alvin M MC. Manual para Estudos Craniométricos e Cranioscópicos. Santa Maria; UFSM 1979: 36-37
• 5 Naguib M B, Aristegui M, Saleh E et al.. Surgical anatomy of the petrous apex as it relates to the enlarged middle cranial fossa approaches.  Otolaryngol Head Neck Surg. 1994;  111 488-493
• 6 Grasek R R. Diagnosis and management of primary tumours of the petrous apex.  Ann Otol Rhinol Laryngol. 1975;  84 1-20
• 7 Fournier H D, Mercier P H, Menei P, Alhayek G, Guy G. Les voies trans-pétreuses dans l′accès au clivus.  Neurochirurgie. 1995;  41 6-28
• 8 Yasargil M G, Fox J L, Ray M W. The operative approach to the aneurysms of the anterior communicating artery. In: Krayenbuhl H Advances and Technical Standards in Neurosurgery. Wien; Springer-Verlag 1975 2: 113-170
• 9 Eisenberg M B, Haddad G, Al-Mefty O. Petrous apex cholesterol granulomas: evolution and management.  J Neurosurg. 1997;  86 822-829
• 10 Brodke J A, Robertson J H, Shea J J, Gardner G. Cholesterol granulomas of the petrous apex: combined neurosurgical and otological management.  J Neurosurg. 1996;  85 625-633
• 11 Harsh G R, Sekhar L N. The subtemporal, transcavernous, anterior transpetrosal approach to the upper brain stem and clivus.  J Neurosurg. 1992;  77 709-717
• 12 Sakata K, Al-Mefty O, Yamamoto I. Venous consideration in petrosal approach: microsurgical anatomy of the temporal bridging vein.  J Neurosurg. 2000;  47 153-161
• 13 Sekhar L N, Schessel D A, Bucur S D, Raso J L, Wright D C. Partial labyrinthectomy petrous apicectomy approach to neoplastic and vascular lesions of the petroclival area.  J Neurosurg. 1999;  44 537-552
• 14 Samii M, Rosahl S K, Tatagiba M S. Microsurgical removal of a petrous apex meningioma after stereotactic radiation. Technical Case Report.  J Neurosurg. 2001;  49 216-220
• 15 Samii M, Tatagiba M, Carvalho G A. Retrosigmoid intradural suprameatal approach to Meckel's cave and the middle fossae: surgical technique and outcome.  J Neurosurg. 2000;  92 235-241
• 16 Schlegel K D, Satravalha S. Epidemiological findings in Indonesia of orthodontic interest.  Anat Anz Jena. 1986;  162 259-269