Facial-zygomatic triangle: a relationship between the extracranial portion of facial nerve and the zygomatic arch.

BACKGROUND: This study was conducted to clarify the relationships between the extracranial portion of the facial nerve (EFN) and the zygomatic arch (ZA). METHOD: Four cadaveric heads (8 parotid regions), examined under 3-40x magnification, were dissected from lateral to medial to expose the EFN. FINDINGS: In a vertical plane just anterior to the tragus, the distance from the superior edge of the ZA to the facial nerve (FN) is, on average, 26.88 mm. The FN then courses superiorly and anteriorly, crossing the ZA 18.65 mm anterior to the tragus on average. Thus, three points can be used to depict a triangle: A, at the level of the anterior border of the tragus, just above the superior edge of the ZA; B, 26 mm below A; and C, 18 mm anterior to A. This so called facial-zygomatic triangle represents the area where surgical dissection can be performed with no risk of damaging the FN. Thus, the closer one stays to the tragus, the lesser the risk of damaging the FN below the ZA. If the incision is carried out on a vertical plane closer to the tragus, the skin can be safely cut up to 2 cm below the ZA. CONCLUSION: The facial-zygomatic triangle is a very useful superficial landmark to avoid FN damage when working below the ZA.

Comparison of lateral microsurgical preauricular and anterior endoscopic approaches to the jugular foramen.

INTRODUCTION: This project compares access to the anterolateral part of the jugular foramen provided by the lateral microsurgical preauricular and the anterior endoscopic approaches, and defines the important landmarks involved in each approach. STUDY DESIGN: Cadaveric study. RESULTS: The endoscopic transnasal/transmaxillary transpterygoid corridor provides a less invasive route for selected lesions in the jugular foramen than the traditional open route through the preauricular subtemporal infratemporal fossa approach. However, the anterior endoscopic approach provides a smaller channel to the jugular foramen than the preauricular approach. CONCLUSIONS: The anterior endoscopic approach to the anterolateral part of the jugular foramen is a useful alternative to the lateral microsurgical preauricular approach in carefully selected cases. The vaginal process of the tympanic part of the temporal bone provides a valuable landmark to aid in accessing the jugular foramen in both procedures and can be drilled to open the foramen in the preauricular approach.

Long-term follow-up of radiotherapy for pituitary adenoma: the absence of late recurrence after greater than or equal to 4500 cGy.

Recent literature has suggested that late recurrence of pituitary adenoma after radiotherapy is common. We hypothesized that late failures might be a result of inadequate dose (less than 4500 cGy). To investigate, we analyzed 105 patients treated at our institution between 1965 and 1986 (analysis, 2/89). The minimum observation time was greater than or equal to 5 years in 58% and greater than or equal to 10 years in 30% of the patients. All patients received megavoltage radiotherapy (range, 4200-5500 cGy; mean, 4821 cGy) at a mean dose per fraction of 172 cGy; 100 patients received greater than or equal to 4500 cGy tumor dose. Twenty-nine patients received radiotherapy alone, and 76 had postoperative radiotherapy after frontal craniotomy (20 patients) or transsphenoidal hypophysectomy (56 patients). At presentation, 71% of patients had extrasellar disease, 57% had visual field deficits, and 50% had endocrinopathy. Of patients treated postoperatively, 74% had gross residual disease. Four local failures occurred at 13, 16, 57, and 64 months after postoperative radiotherapy, all within the irradiated volume (tumor doses of 4700, 4715, 5000, and 5100 cGy). All four patients had presented with moderate to extensive extrasellar disease with visual field defects. Two of the four remain free of second recurrence at 7 and 13 years after salvage transsphenoidal hypophysectomy. The local control rate with radiotherapy (product-limit method) at 10 years was 100% in the radiotherapy-alone group and 92% in the postoperative radiotherapy group (95% for all patients). To prevent bias, seven patients who received bromocriptine, none of whom demonstrated a recurrence, were censored from the local control analysis at the initiation of the drug. No patient in this study suffered recurrence greater than 64 months after radiotherapy, with 31 patients (none with bromocriptine) observed 10 to 21 years. We conclude that treatment of pituitary adenoma with greater than or equal to 4500 cGy in 25 fractions can result in a high (greater than or equal to 90%) probability of stable long-term control.

Benign meningiomas: primary treatment selection affects survival.

PURPOSE: To examine the effect of primary treatment selection on outcomes for benign intracranial meningiomas at the University of Florida. METHODS AND MATERIALS: For 262 patients, the impact of age, Karnofsky performance status, pathologic features, tumor size, tumor location, and treatment modality on local control and cause-specific survival was analyzed (minimum potential follow-up, 2 years; median follow-up, 8.2 years). Extent of surgery was classified by Simpson grade. Treatment groups: surgery alone (n = 229), surgery and postoperative radiotherapy (RT) (n = 21), RT alone (n = 7), radiosurgery alone (n = 5). Survival analysis: Kaplan-Meier method with univariate and multivariate analysis. RESULTS: At 15 years, local control was 76% after total excision (TE) and 87% after subtotal excision plus RT (SE+RT), both significantly better (p = 0.0001) than after SE alone (30%). Cause-specific survival at 15 years was reduced after treatment with SE alone (51%), compared with TE (88%) or SE+RT (86%) (p = 0.0003). Recurrence after primary treatment portended decreased survival, independent of initial treatment group or salvage treatment selection (p = 0.001). Atypical pathologic features predicted reduced 15-year local control (54 vs. 71%) and cause-specific survival rates (57 vs. 86%). Multivariate analysis for cause-specific survival revealed treatment group (SE vs. others; p = 0.0001), pathologic features (atypical vs. typical;p = 0.0056), and Karnofsky performance status (> or = 80 vs. < 80; p = 0.0153) as significant variables. CONCLUSION: Benign meningiomas are well managed by TE or SE+RT. SE alone is inadequate therapy and adversely affects cause-specific survival. Atypical pathologic features predict a poorer outcome, suggesting possible benefit from more aggressive treatment. Because local recurrence portends lower survival rates, primary treatment choice is important.

Radiotherapy for pituitary adenoma: long-term outcome and sequelae.

PURPOSE: To review outcome and treatment sequelae in patients treated with external beam radiotherapy for pituitary adenomas. METHODS AND MATERIALS: One hundred forty-one patients with pituitary adenomas received radiotherapy at the University of Florida and had 2-year minimum potential follow-up. One hundred twenty-one had newly diagnosed adenomas, and 20 had recurrent tumors. Newly diagnosed tumors were treated with surgery and radiotherapy (n = 98) or radiotherapy alone (n = 23). Patients with recurrent tumors received salvage treatment with surgery and radiotherapy (n = 10) or radiotherapy alone (n = 10). The impact of age, sex, presenting symptoms, tumor extent, surgery type, degree of resection, hormonal activity, primary or salvage therapy, and radiotherapy dose on tumor control was analyzed. Tumor control is defined by the absence of radiographic progression and stable or decreased hormone level (in hormonally active tumors) after treatment. Effect of therapy on vision, hormonal function, neurocognitive function, life satisfaction, and affective symptoms were examined. A Likert categorical scale survey was used for assessment of neurocognitive, life satisfaction, and affective symptom status. Survey results from the radiotherapy patients were compared with a control group treated with transsphenoidal surgery alone. Multivariate analysis used the forward step-wise sequence of chi squares for the log rank test. RESULTS: At 10 years, tumor control for the surgery and radiotherapy group (S + RT) was 95% and not statistically different (p = 0.58) than for patients treated with radiotherapy alone (RT) (90%). Patients with prolactin- and ACTH-secreting tumors had significantly worse tumor control, as did patients treated for recurrent tumors. Multivariate analysis for tumor control revealed that only young age was predictive of worse outcome (p = 0.0354). Visual function was either unaffected or improved in most patients, although four patients developed visual loss due to treatment. Hormonal function was affected adversely in 46 of the 93 patients for whom detailed hormonal information was available. Neurocognitive function evaluation revealed that patients in the S + RT group were more likely (p = 0.005) to report difficulty with memory than those in the RT-alone or S-alone groups. No significant difference in life satisfaction or affective symptoms was evident. CONCLUSIONS: Pituitary adenomas are well controlled by external beam radiotherapy, either alone or in combination with surgery. Visual symptoms often improve after treatment. Hormonal sequelae require medical intervention in many patients. Neurocognitive sequelae may be different among treatment groups.

The suboccipital approach to removal of acoustic neuromas.

This article reviews the author's technique for removing acoustic neuromas by the suboccipital approach. Also discussed are various considerations regarding the selection and use of instruments for this operation. The anatomy of the internal acoustic meatus and the principles involved in facial- and cochlear-nerve preservation are described. A guide is provided for stepwise dissection of the internal acoustic meatus in the laboratory.

Accessory light for the surgical microscope.

This report describes a new accessory fiberoptic light for the most widely used surgical microscope. The advantages of this light are that it permits easy sterile draping of the microscope, does not require a special lens cover, can be adjusted to vary the size and location of the field of illumination, and produces minimal interference with the passage of microinstruments into the operative exposure.

Neurosurgery at the University of Florida.

The significant factors in the development of the neurosurgery program at the University of Florida have been the funding for 10 endowed chairs and a Brain Institute, the achievement of departmental status in the College of Medicine, the collaborative research with a strong Department of Neuroscience, and the strong commitment by the faculty to subspecialty neurosurgery and to service in the national neurosurgical organizations.

Microsurgical anatomy of the superior orbital fissure.

The microsurgical anatomy of the superior orbital fissure was examined in cadaver specimens. The cavernous sinus fills the posterior margin and the orbital contents fill the anterior margin of the fissure. All of the nerves coursing in the walls of the cavernous sinus pass through the superior orbital fissure to reach the orbit. The fissure has a narrow lateral part and a larger medial part. The annular tendon from which the rectus muscles arise is situated in front of the upper half of the medial part of the fissure and is attached to the lateral margin near the junction of the lateral and medial parts. The fissure is divided into three sectors: lateral, central, and inferior. The lateral sector, which corresponds to the narrow lateral part, transmits the trochlear, frontal, and lacrimal nerves and the superior ophthalmic vein, all of which course outside the annular tendon. The central sector, which is situated behind and is aligned with the lateral part of the annular tendon, transmits the superior and inferior divisions of the oculomotor nerve, the abducens and nasociliary nerves, and the sensory and sympathetic roots of the ciliary ganglion, all of which pass through the annular tendon. The inferior sector, which is located below the annular tendon and origin of the inferior rectus muscle, is filled with a posterior extension of the orbital fat and transmits the inferior ophthalmic vein. The relationship and course of the nerves in each sector and the incisions that may be used to open and expose the contents of the fissure are reviewed.

Unilateral upper and lower subtotal maxillectomy approaches to the cranial base: microsurgical anatomy.

OBJECTIVE: The relationship of the maxilla, with its thin walls, to the nasal and oral cavities, the orbit, and the infratemporal and pterygopalatine fossae makes it a suitable route for accessing lesions involving both the central and lateral cranial base. In this study, we compared the surgical anatomy and exposure obtained by two unilateral transmaxillary approaches, one directed through an upper subtotal maxillectomy, and the other through a lower subtotal maxillectomy. METHODS: Cadaveric specimens examined, with 3 to 40x magnification, provided the material for this study. RESULTS: Both upper and lower maxillectomy approaches open a surgical field extending from the ipsilateral internal carotid artery to the contralateral Eustachian tube; however, they differ in the direction of the access and the areas exposed. The lower maxillectomy opens a combination of the transmaxillary, transnasal, and transoral routes to extra- and intradural lesions of the central cranial base. Performing additional osteotomies of the mandibular coronoid process and the sphenoid pterygoid process provides anterolateral access to the lateral cranial base, including the pterygopalatine and infratemporal fossae, and the parapharyngeal space. The upper maxillectomy opens the transmaxillary and transnasal routes to the central cranial base but not the transoral route. The structures exposed in the lateral cranial base, after removing the coronoid and pterygoid processes, include the pterygopalatine and infratemporal fossae and the parapharyngeal space. Exposure can be extended by a frontotemporal craniotomy, which provides access to the anterior and middle cranial fossae and the basal cisterns. CONCLUSION: The upper and lower subtotal maxillectomy approaches provide wide but differing access to large parts of the central and lateral cranial base depending on the site of the osteotomies.

Middle meningeal origin of the ophthalmic artery.

OBJECTIVE: To examine the microsurgical anatomy and clinical significance of an anomalous origin of the ophthalmic artery from the middle meningeal artery. METHODS: In the course of an anatomic study of the cavernous sinus, an anomalous ophthalmic artery arising from the middle meningeal artery was found. To further define the anatomy of the region, five additional skulls, in which the arteries and veins were injected with colored latex, were dissected using 3x to 40x magnification. RESULTS: The anomalous ophthalmic artery arose from the frontal branch of the middle meningeal artery, passed through the superior orbital fissure, and supplied the entire contents of the orbit, as well as giving rise to the central retinal artery. This study provides the first display of this anomaly in an anatomic dissection. CONCLUSION: The ophthalmic artery may infrequently arise from the middle meningeal artery. This anomaly places the ophthalmic artery at risk during procedures in which the dura is elevated from the greater and lesser wings of the sphenoid or when the sphenoid ridge is removed and during embolization procedures involving the branches of the external carotid artery.

Suprameatal extension of the retrosigmoid approach: microsurgical anatomy.

OBJECTIVE: This study was conducted to determine whether removing the bony prominence located above the porus of the internal acoustic meatus, called the suprameatal tubercle, and surrounding bone using the retrosigmoid approach would aid in the exposure of tumors that are located predominantly in the cerebellopontine angle but that also extend into the middle cranial fossa in the region of Meckel's cave and thus avoid the need for a supratentorial craniotomy. METHODS: Thirty cerebellopontine angles from 15 cadaveric heads examined using 3 to 40x magnification provided the material for this study. A retrosigmoid craniotomy was completed and the exposure obtained before and after removing the suprameatal tubercle, and the surrounding bone was examined. In some cases, Meckel's cave and the tentorium lateral to the porus of Meckel's cave was opened to aid in the exposure. RESULTS: Removing the suprameatal tubercle and surrounding bone increased the exposure an average of 10.3 mm (range, 8.0-13.0 mm) forward of the exposure, which could be obtained without suprameatal drilling. The extent of bone removal was limited on the lateral side by the posterior and superior semicircular canals and their common crus. CONCLUSION: The suprameatal extension of the retrosigmoid approach will permit removal of some tumors that are located mainly in the posterior fossa but that extend into the middle fossa in the region of Meckel's cave. The exposure can be increased by opening the superior petrosal sinus as it crosses in the upper margin of the porus of Meckel's cave and by opening the tentorium lateral to Meckel's cave.

Microsurgical anatomy of the posterior fossa cisterns.

The microsurgical anatomy of the posterior fossa cisterns was examined in 15 cadavers using 3X to 40X magnification. Liliequist's membrane was found to split into two arachnoidal sheets as it spreads upward from the dorsum sellae: an upper sheet, called the diencephalic membrane, which attaches to the diencephalon at the posterior edge of the mamillary bodies, and a lower sheet, called the mesencephalic membrane, which attaches along the junction of the midbrain and pons. Several other arachnoidal membranes that separate the cisterns were identified. These include the anterior pontine membrane, which separates the prepontine and cerebellopontine cisterns; the lateral pontomesencephalic membrane, which separates the ambient and cerebellopontine cisterns; the medial pontomedullary membrane, which separates the premedullary and prepontine cisterns; and the lateral pontomedullary membrane, which separates the cerebellopontine and cerebellomedullary cisterns. The three cisterns in which the arachnoid trabeculae and membranes are the most dense and present the greatest obstacle at operation are the interpeduncular and quadrigeminal cisterns and the cisterna magna. Numerous arachnoid membranes were found to intersect the oculomotor nerves. The neural and vascular structures in each cistern are reviewed.

The jugular foramen: microsurgical anatomy and operative approaches.

The jugular foramen, based on these studies of microsurgical anatomy, is divided into three compartments: two venous and a neural or intrajugular compartment. The venous compartments consist of a larger posterolateral venous channel, the sigmoid part, which receives the flow of the sigmoid sinus, and a smaller anteromedial venous channel, the petrosal part, which receives the drainage of the inferior petrosal sinus. The petrosal part forms a characteristic venous confluens by also receiving tributaries from the hypoglossal canal, petroclival fissure, and vertebral venous plexus. The petrosal part empties into the sigmoid part through an opening in the medial wall of the jugular bulb between the glossopharyngeal nerve anteriorly and the vagus and accessory nerves posteriorly. The intrajugular or neural part, through which the glossopharyngeal, vagus, and accessory nerves course, is located between the sigmoid and petrosal parts at the site of the intrajugular processes of the temporal and occipital bones, which are joined by a fibrous or osseous bridge. The glossopharyngeal, vagus, and accessory nerves penetrate the dura on the medial margin of the intrajugular process of the temporal bone to reach the medial wall of the internal jugular vein. The operative approaches, which access the foramen and adjacent areas and are demonstrated in a stepwise manner, are the postauricular transtemporal, retrosigmoid, extreme lateral transcondylar, and preauricular subtemporal-infratemporal approaches.

Modified supraorbital craniotomy: technical note.

The authors present a surgical approach that incorporates the frontal sinus and extends a supraorbital craniotomy to include the lateral orbital rim and zygoma. The craniotomy provides wide exposure of the anterior fossa, orbit, ipsilateral middle fossa, and cavernous sinus. The procedure can be performed easily, and the bone flaps can be secured rapidly back into the anatomical position at the time of closure. This modified supraorbital craniotomy is ideal for large benign lesions originating along the sphenoid wing or orbit that expand into the anterior fossa.

Microsurgery of the third ventricle: Part I. Microsurgical anatomy.

The 3rd ventricle is one of the most surgically inaccessible areas in the brain. It is impossible to reach its cavity without incising some neural structures. Twenty-five cadaveric brains were examined in detail to evaluate the surgically important relationships of the walls of the 3rd ventricle. The routes through which the 3rd ventricle can be reached are (a) from above, through the foramen of Monro and the roof after entering the lateral ventricle through the corpus callosum or the cerebral cortex; (b) from anterior, through the lamina terminalis; (c) from below, through the floor if it has been stretched by tumor; and (d) from posterior, through the pineal region or from the posterior part of the lateral ventricle through the crus of the fornix. The posterior part of the circle of Willis and the basilar artery are intimately related to the floor, the anterior part of the circle of Willis and the anterior cerebral and anterior communicating arteries are related to the anterior wall, and the posterior cerebral artery supplies the posterior wall. The deep cerebral venous system is intimately related to the 3rd ventricle; the internal cerebral vein is related to the roof, and the basal vein is related to the floor. The junction of these veins with the great veins forms a formidable obstacle to the operative approach to the pineal gland and the posterior part of the 3rd ventricle.

Microsurgery of the third ventricle: Part 2. Operative approaches.

The operative approaches to the 3rd ventricle are divided on the basis of whether they are suitable for reaching the anterior or posterior part of the 3rd ventricle. The approaches suitable for lesions within or compressing the anterior portion of the 3rd ventricle are the trans-sphenoidal, subfrontal, frontotemporal, subtemporal, anterior transcallosal, and anterior transventricular. The approaches suitable for reaching the posterior portion of the 3rd ventricle are the posterior transcallosal, posterior transventricular, occipital transtentorial, and infratentorial supracerebellar. Considerations important in selecting one of these approaches are reviewed.

Microsurgery of the fourth ventricle: Part 1. Microsurgical anatomy.

Operations on the 4th ventricle offer the potential for injury of the brain stem, cerebellum, cranial nerves, and major cerebellar arteries and veins. Twenty-five cadaver brains were examined using 3x to 25x magnification to define the relationship of these vital structures to the 4th ventricle. The 4th ventricle has a roof, a floor, and two lateral recesses. Most of the cranial nerves arise near the floor, which sits on the pons and medulla. The superior half of the roof, formed by the superior medullary velum, lingula, and cerebellar peduncles, is intimately related to the cerebellomesencephalic fissure, the superior cerebellar arteries, and the vein of the cerebellomesencephalic fissure. The inferior half of the roof, formed by the inferior medullary velum, tela choroidea, nodule, and uvula, is intimately related to the cerebellomedullary fissure, the posterior inferior cerebellar arteries, and the veins of the cerebellomedullary fissure. The lateral recesses and adjoining parts of the roof and floor are intimately related to the cerebellopontine fissures, the anterior inferior cerebellar arteries, and the veins of the cerebellopontine fissure. The cerebellar peduncles converge on and form a major part of the ventricular surface. The hili of the dentate nuclei abut on the superolateral recesses of the ventricle near the superior poles of the tonsils.

Microsurgical anatomy and operative approaches to the lateral ventricles.

The anatomy needed to plan microoperative approaches to the lateral ventricles was examined in 20 cadaveric cerebral hemispheres. The neural, arterial, and venous structures in the walls of the lateral ventricles and the relationship of the lateral ventricles to the third ventricle and basal cisterns were examined. The operative approaches to the lateral ventricle are reviewed.

Microsurgical anatomy of the dural collar (carotid collar) and rings around the clinoid segment of the internal carotid artery.

OBJECTIVE: To examine the relationship of the clinoid segment of the internal carotid artery to the structures in the roof of the cavernous sinus and to determine whether this segment is neither intradural nor intracavernous, as recently proposed. METHODS: The region of the roof of the cavernous sinus was dissected and examined using 3 to 40x magnification and micro-operative techniques. RESULTS: The clinoid segment was located within a collar formed by the dura lining the medial surface of the anterior clinoid process, the posterior surface of the optic strut, and the upper part of the carotid sulcus. The clinoid segment and the collar were defined above by the upper ring formed by the dura extending medially from the upper surface of the anterior clinoid process to surround the artery and below by the lower ring formed by the dura extending medially from the lower surface of the anterior clinoid process. The upper ring was adherent to the wall of the artery, but the lower dural ring was separated from the lower margin of the clinoid segment by a narrow space that admitted venous tributaries of the cavernous sinus, called the clinoid venous plexus. This venous plexus narrowed as the upper ring was approached and became wider at the lower ring, where the plexus communicated with the venous channels of the cavernous sinus. The upper and lower dural rings were best defined along the lateral and anterior margins of the artery, were less distinct medially, and disappeared posteriorly, where the dura forming the upper and lower rings came together. CONCLUSION: The clinoid segment is intracavernous, being located within a collar of dura in which venous tributaries of the cavernous sinus course. The implications of these findings for surgery are reviewed.