Meckel's cave.

OBJECTIVE: To review the microsurgical anatomy of Meckel's cave, a detailed knowledge of which is a prerequisite to devising an appropriate surgical strategy and performing successful surgery. METHODS: The microsurgical anatomy of Meckel's cave was studied under an operating microscope in 15 human cadaver heads (30 sides). To understand the meningeal architecture and the cross-sectional anatomy of Meckel's cave, serial histologic sections were made in an additional adult human cadaver specimen. RESULTS: Meckel's cave is a natural mouth-shaped aperture connecting with the posterior fossa that is located in the medial portion of the middle cranial fossa. The cave extends forward similar to an open-ended three-fingered glove and provides a channel for the rootlets of the trigeminal nerve; the trigeminal ganglion; and the ophthalmic (cranial nerve V(1)), maxillary (cranial nerve V(2)), and mandibular (cranial nerve V(3)) divisions until they reach their respective foramina. The average height of this oval mouth was found to be 4.2 mm (range 3-5 mm) and the average width was 7.6 mm (range 6-8 mm). The mouth of Meckel's cave was located 12 mm (range 10-15 mm) superior and medial to the internal acoustic meatus and 6.5 mm (range 5-8 mm) superior and medial to the dural point of entrance of the nervus abducens and 20 mm (range 18-23 mm) medial to the arcuate eminence. CONCLUSIONS: Detailed and sound knowledge of the microsurgical anatomy of Meckel's cave, which borders on surgically important structures, such as the internal carotid artery and cavernous sinus, is essential to performing precise microneurosurgery in this region. This study describes the complex anatomy of Meckel's cave and surrounding structures to provide the knowledge needed to devise a more complete surgical strategy and establish accurate orientation during the surgical procedure.

The microsurgical anatomy of the hypoglossal canal.

BACKGROUND: The hypoglossal canal (HC) is a region of the skull base whose involvement in many pathological entities is often ignored. Adequate knowledge of the anatomy of the HC and its related bony, neural, and vascular structures is essential for surgery of lesions involving this area. METHODS: Ten adult human cadaver heads from a US source fixed by formalin (20 sides) and 20 dry human skulls from Indian sources (40 sides) were used in this study. Various aspects of the anatomy of this region including the size, course and variation of the hypoglossal nerve and its relationship to the adjacent and canalicular course were recorded. RESULTS: The left HC was located at 10 o'clock and the right HC at the 2 o'clock position with respect to the foramen magnum. The canal was surrounded superiorly by the jugular tubercle, superolaterally by the jugular foramen, laterally by the sigmoid sinus and inferiorly by the occipital condyle. All dry skulls were drilled in the horizontal plane at an axis of about 45 degrees and directed slightly upwards. CONCLUSIONS: Detailed knowledge of the microsurgical anatomy of the region of the HC is crucial when performing surgery for lesions of the condylar region, the lower clivus, and ventral brain stem. This study provides the knowledge required to achieve accurate orientation and effective maneuvers during surgical procedures for treatment of the patient without injuring the vital neural and bony structures.

Risky anatomic variations of sphenoid sinus for surgery.

We searched for the surgically risky anatomic variations of sphenoid sinus and aimed to compare axial and coronal tomography in detection of these variations. Fifty-six paranasal tomography images (112 sides) were evaluated for coronal, axial and both coronal and axial images. Tomographic findings including bony septum extending to optic canal or internal carotid artery; protrusions and dehiscences of the walls of internal carotid artery, optic nerve, maxillary nerve and vidian nerve; extreme medial course of internal carotid artery; patterns of aeration of the anterior clinoid process; and Onodi cells were evaluated. The results were classified as "present, absent, suspicious-thin (only for dehiscence) or no-consensus". The results of each plane were compared with that of the result of the both planes together. Kappa coefficient and Chi-square tests were used to compare both planes. Twelve cadaveric dissections were performed to reveal the proximity of sphenoid sinus to surgically risky anatomic structures. Endoscopy was applied to five cadavers. 18 evaluations were classified as 'no-consensus'. We detected 34, 35, 34 and 40 protrusions of internal carotid artery, optic nerve, maxillary nerve, vidian nerve, respectively. Dehiscences were present in 6, 9, 4 and 8, and suspicious-thin in 8, 10, 16 and 25 in canals of internal carotid artery, optic nerve, maxillary nerve and vidian nerve, respectively. Bony septum to internal carotid artery and optic nerve was observed in 30 and 22 cases. We observed 9 extreme medial courses of internal carotid artery, 27 aerated clinoid process and 9 Onodi cells. Axial images were superior in detection of bony septum to internal carotid artery and Onodi cells; while the coronal images were more successful in detection of protrusion of optic nerve and vidian nerve, and dehiscense of maxillary nerve and vidian nerve (P<0.05). In cadaveric dissections, the septa were inserted into the bony covering of the carotid arteries in two sinuses (8.3%). Detailed preoperative analysis of the anatomy of the sphenoid sinus and its boundaries is crucial in facilitating entry to the pituitary fossa and reducing intraoperative complications. Coronal tomography more successfully detects the sphenoid sinus anatomic variations.

Prevalence of primary tethered cord syndrome associated with occult spinal dysraphism in primary school children in Turkey.

The prevalence and associated factors of primary tethered cord syndrome (PTCS) in primary school children were investigated. A cross-sectional study was performed in four demographically different primary schools in Turkey. Demographic, familial and physical data were collected from 5,499 children based on enuresis as a predominant symptom and dermatologic and orthopedic signs as clues of occult spinal dysraphism. Statistical analysis and input of the data were carried out with the SPSS package program 10.00, and logistic regression analysis was used to identify discriminating factors between enuretic children with or without neurologic signs. Of 5,499 analyzed children, 422 (7.7%) had enuresis nocturna, and 19.9% of 422 children had also daytime incontinence. Sixteen of these 422 enuretic children (3.8%) had several dermatologic signs. Five of them had spina bifida on plain radiographies, and 4 of them had cord tethering on lumbar MRI. Fifteen of 422 enuretic children (3.7%) had gait disturbances and orthopedic anomalies without cutaneous manifestations. Six of 15 children had spina bifida on plain graphies and 2 of them had tethered cord syndrome on MRI. The general prevalence of PTCS was found to be 0.1% of 5,499 analyzed children and 1.4% of enuretic children. A good outcome after untethering was found in 83.0% in this series. Practitioners should be aware of these clues of occult spinal dysraphism and resort to further radiologic and neurosurgical assessment. Early surgical intervention may halt the progression of the neurologic deficits and stabilize or reverse symptoms.

Comparison of the exposure obtained by endoscope and microscope in the extended trans-sphenoidal approach.

OBJECTIVE: Trans-sphenoidal surgery is often combined with other approaches for the treatment of middle cranial base tumors. By combining a maxillotomy with trans-sphenoidal approach, significantly wider exposure to these regions is gained. However, endoscope-assisted techniques have also been used for sellar and parasellar and upper clival regions. METHODS: An extended trans-sphenoidal approach was performed on 10 cadaver heads using the operating microscope and was repeated with a 0-degree endoscope. The mean horizontal and vertical distances were measured and pictured for each technique, and both distances were compared using a parametric paired Student's t-test. RESULTS: The mean horizontal distances in the 10 specimens were 19.5 +/- 1.8 mm by microscope and 27.5 +/- 2.2 mm by endoscope, and the mean vertical distances were 25.8 +/- 1.9 mm by the microscope and 34.5 +/- 3.5 mm by the endoscope. CONCLUSION: The aim of this study was to quantify the amount of exposure obtained with an extended trans-sphenoidal approach and to compare both endoscopic and microscopic techniques. Using the endoscope in conjunction with the operating microscope may provide additional exposure and better access in skull base surgery.