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Middle cranial fossa arachnoid cysts causing sensorineural hearing loss.

Arachnoid cyst of the middle cranial fossa has never been reported to present with sensorineural hearing impairment. We report the case of a 15-year-old girl who complained of progressive hearing loss on the right side for 4 years. The pure tone audiometry revealed sensorineural hearing loss with an average of 63 dB, and the auditory brain stem response demonstrated absence of all waves on the right side. Magnetic resonance imaging showed giant arachnoid cysts occupying the bilateral middle cranial fossa and extending to the parietal and prepontine areas with the atrophic change of the right facial-acoustic nerve cord and a decrease in signal intensity of the right cochlea and vestibule. The cystoperitoneal shunting procedure was suggested, but the parents hesitated about the surgical treatment. The patient has not received any surgical intervention, and her hearing has been stable for 1 year during the follow-up period. This case represents the first report that sensorineural hearing loss is a possible presenting symptom when arachnoid cysts of the middle cranial fossa are massive.

Adolescent↗

Fracture of the glenoid fossa and dislocation of the mandibular condyle into the middle cranial fossa.

Reported cases of dislocation of the mandibular condyle into the middle cranial fossa have been rare, and treatment modalities have varied. The case presented represents an instance of successful closed reduction. Numerous factors should be considered when determining the technique of reduction. Primary goals in selecting the method of treatment are stabilization of the neurologic status, control of the bone fragments in the brain, reduction of the occlusion, maintenance of ramus height for facial symmetry, preservation of growth potential, and assurance of satisfactory long-term function of the mandible.

Child↗

[The extended middle cranial fossa approach: a morphometric analysis].

The extended middle cranial fossa (EMCF) approach calls for removal of the petrous bone from its subtemporal surface in order to well expose the internal auditory canal (IAC) and the posterior fossa dura (PDF) around its meatus, safeguarding, at the same time, all the important, closely related, anatomical structures (the Gasserian ganglion (GG) and its third trigeminal division, the internal carotid artery (ICA), the cochlea, the posterior labyrinth, the superior petrosal sinus (SPS), the inferior petrosal sinus (IPS) and the jugular bulb (JB). The middle meningeal artery, on the other hand, could be divided when necessary. We dissected 25 temporal bones preserved in formaldehyde and those of five cadavers in order to define the limits of this approach. Measurements were taken so as to establish the limits of the approach as well as to determine the most appropriate angles and distances in working in this area. As previously suggested by the Senior Author (MS), we found it safer to start working medially in order to identify the IAC and then to extend the dissection laterally. The most constant angle proved to be that between the IAC and the SPS. The distances and areas found appear to be highly variable and difficult to rely upon. A thorough knowledge of this anatomy is of most importance for the surgeon who intends to use this approach.

Brain↗

Acoustic neuroma surgery. Translabyrinthine-transtentorial approach via the middle cranial fossa.

In our approach for acoustic tumors, the method of Morrison and King and that of Bochenek and Kukwa have been modified into one method. This modified method is basically a neuro-otological-neurosurgical team approach, extending the operative field by drilling the temporal bone and cutting the superior petrosal sinus, tentorium, and posterior fossa dura according to the size of the tumor. Therefore, for tumors slightly protruding into the posterior fossa from the prous of the internal auditory canal, only the bone adjacent to it is removed (Bochenek et al's method). For larger tumors, labyrinthectomy and mastoidectomy with the separation of the superior petrosal sinus and the tentorium and posterior fossa dura are also performed. In Morrison et al.'s method, the translabyrinthine approach is done first and the middle cranial fossa approach is performed thereafter. In contrast, in the modified method, drilling the bone from the middle cranial fossa to the tip of the mastoid--labyrinthectomy and mastoidectomy--is the first thing done after elevating the temporal lobe and revealing the middle cranial fossa, and the internal auditory canal is opened thereafter. Thirty-five cases of acoustic tumors and other cerebello-pontine angle tumors were operated on during the past 3.5 years through the middle cranial fossa. Among 30 cases of acoustic tumors, eight cases in which the tumors were confined to the internal auditory canal were operated on through the middle cranial fossa. In four cases, Bochenek et al's method was performed in which bones adjacent to the internal auditory canal and a part of the labyrinth are removed without cutting the superior petrosal sinus. In 23 cases including five cerebellopontine angle tumors, the modified translabyrinthine-transtentorial approach through the middle cranial fossa was done. This modification has the advantage that severe postoperative complications are less frequent. The surgical technique and the results are discussed.

Adolescent↗

Identification of internal acoustic canal in the middle cranial fossa approach: a safe technique.

BACKGROUND: The middle cranial fossa approach (MCFA) is a very valuable functional approach in the armamentarium of the neuro-otologic surgeon. Identification of the internal acoustic canal (IAC) in MCFA is one of the most tedious steps. Many techniques have been described to locate the IAC safely when using the MCFA. OBJECTIVE: We sought to describe a safe technique for identification of the IAC and to demonstrate its feasibility in temporal bone dissections, as well as to discuss our clinical experience with this technique. METHODS: The surgical anatomy of the 20 temporal bones were evaluated and measured, especially by defining the medial and lateral ends of the IAC and relations to the nearby located structures. Measurements were obtained at 3 levels: the width of the IAC at the level of the fundus, the width of the IAC at the level of the porus, and the safe distance around the IAC at the meatal level. The medial and lateral IAC end widths were compared with each other and with the safe area at the meatal level. RESULTS: The smallest, the largest, and the mean values were recorded. The mean width of the IAC at the level of the porus was found to be more than 3-fold that of the width of the IAC at the level of the Bill's bar, and the ratio between the width of the medial safe area around the IAC and the lateral end of the IAC was found to be more than 7-fold as wide. CONCLUSION: This technique offers direct quick exposure of the IAC, without handling the facial nerve and the inner ear structures. Forty-five cases of operations with the same technique showed excellent ease and safety of identifying the IAC medially in the MCFA.

Craniotomy↗

[Clinical study of lacrimal gland tumor involving anterior and middle cranial fossae].

OBJECTIVE: To investigate the clinical manifestations of lacrimal gland tumor involving the anterior and middle cranial fossae and the effect of transcranial-orbital approach in treatment of such tumor. METHODS: A retrospective study was conducted on the clinical data of 23 cases lacrimal gland tumor involving the anterior and middle cranial fossae confirmed by radiological examination, including 11 cases of adenoid cystic carcinoma, 6 cases of pleomorphic adenocarcinoma (malignant mixed tumor), 2 cases of adenocarcinoma, 1 case of squamous cell carcinoma, 1 case of ductal carcinoma, 1 case of mucoepidermoid carcinoma, and 1 case of benign mixed tumor, 15 males and 8 females, aged 42.5 (2 - 76), with a case history of 43 months (2 months to 27 years), with the chief complaints of progressive proptosis, disgenesia of the eye ball, and orbit pain, all undergoing transcranial-orbital operation from August 1998 to February. 2006. Follow up was conducted for 1 month to 7 years. RESULTS: Postoperatively, ophthalmoplegia was found in 4 cases, and blindness in 1 case. There was no operative death or other significant complication. Recurrence of tumor occurred in 4 cases, and 1 case died from distant metastasis of adenocarcinoma. CONCLUSIONS: Malignant lacrimal gland tumors, mainly adenoid cystic carcinomas, incline to involve the anterior and middle cranial fossae. Adequate orbital apex decompression and exposure of the tumor can result from suitable transcranial-orbital approach. However, complete surgical excision is difficult, and the tumor has a tendency to recur post-operatively. Suitable treatment strategy should by combination of operation with irradiation or chemotherapy. Prognosis is poor.

Adolescent↗

Facial nerve function after surgery for removal of acoustic neuroma by the extended middle cranial fossa approach.

Postoperative facial nerve function was evaluated in 98 patients operated on by the middle cranial fossa approach or the extended middle cranial fossa approach from June 1976 to April 1985. In this series, the smaller the tumor size at the time of the initial surgery, the better the postoperative facial nerve function was. The facial nerve was preserved in 83.4% of the 79 patients who were subjected only to the initial surgery. However, total removal of the tumor along with facial nerve preservation was achieved only in 70.8%. Anatomical preservation of the facial nerve was possible in 78% of 87 patients. The postoperative functional results among patients in whom facial nerves were anatomically preserved were satisfactory (facial expression score of 75% or higher, i.e., 30 points or more out of a possible 40 points) in 70-80% of the patients with small size or intracanalicular tumors, but, in less than 50% of the patients with tumors of medium size or larger. There is a need to obtain higher rates of functional preservation as well as higher rates of satisfactory functional results. At the present stage, we must strive to achieve earlier diagnosis so that surgery can be performed while the tumor is still medium-sized or small.

Adult↗

Dangerous angles and depths for middle ear and middle cranial fossa injury during arthroscopy of the temporomandibular joint.

PURPOSE: Several reports have suggested a risk of injury to the middle cranial fossa and middle ear during arthroscopic procedures in the superior joint space of the temporomandibular joint (TMJ). However, there has been no anatomic study of directions and distances of the TMJ from the posterior portal in relation to the risk of mandibular fossa injury. In this study, the angles and depths at which the risk is greatest for injury to the deepest point of the mandibular fossa (DP) and to the middle ear during arthroscopy were analyzed. MATERIALS AND METHODS: Three-dimensional measurements of 96 mandibular fossae in 48 dry skulls were made. RESULTS: It was found that the distance from the lateral rim of the fossa to DP and Hugier's canal was 9.50 +/- 2.07 mm and 17.04 +/- 3.09 mm, respectively. The most dangerous angle for DP injury in the Frankfort horizontal plane (FH plane) was an inclination of the instrument base of -8 degrees dorsad and 17 and 19 degrees caudad in the frontal plane. The most dangerous angle for Hugier's canal injury was a tilting of the instrument base of 15 degrees ventrad in the FH plane and -2 degrees craniad in the frontal plane. However, these values showed a wide range. CONCLUSION: It was concluded that great care must be exercised in manipulation of instruments near the DP and Hugier's canal to avoid injury to the middle ear or penetration into the middle cranial fossa.

Adolescent↗

[A case of middle cranial fossa meningioma extending into the infratemporal fossa: an approach to the pterygoid extension of the sphenoid sinus via the infratemporal fossa].

A case of middle cranial fossa meningioma extending into infratemporal fossa and the pterygoid process is presented. The patient had a sphenoid sinus extending inferolaterally into the pterygoid process, which is known as pterygoid extension of the sphenoid sinus. This type of variation of the sphenoid sinus allowed a safe and well-oriented approach to the pterygoid process via the infratemporal fossa. The tumor extending into the pterygoid process was removed successfully without damaging any surrounding structures, e.g. maxillary nerve or Vidian nerve. However, pterygoid extension of the sinus is seen in only 40% of cases. Therefore, close preoperative examination with bone window CT scan is mandatory before employing this approach.

Cranial Fossa, Posterior↗

Condylar penetration into the middle cranial fossa.

This article describes two cases of condylar penetration into the middle cranial fossa in which a similar surgical procedure is used, namely, a rib graft for closure of the fossa. The rib graft, being an autogenous substance, does not present the problems associated with alloplastic materials. If care is taken not to contaminate the graft, and if the bone used has adequate thickness to prevent penetration and resorption, the graft will prove a superior option to repair damage in the middle cranial fossa.

Adult↗

Arachnoid cysts of the middle cranial fossa: experience with 77 cases treated surgically.

Arachnoid cysts of the middle cranial fossa (Sylvian cysts), represent the most common type of intracranial leptomeningeal malformation. Among the 102 intracranial arachnoid cysts operated on at the authors' institution from January 1970 to August 1986, the 77 cases (75%) located in the middle cranial fossa are reviewed. The higher incidence in the first two decades of life (51 cases) as well as the marked predilection for the male sex (60 cases) and the left hemisphere (55 cases) are confirmed in the authors' experience. As for clinical presentation cranial deformities, symptoms of raised intracranial pressure and epilepsy constituted the most frequent features. In 13 patients a complicating lesion was associated: subdural or intracystic haematomas in 7 cases, subdural hygromas in 4 cases and, extradural haematomas in 2 cases. Based on the appearance at CT scan and the results at CT cisternography the authors proposed a classification into three basic types of increasing severity and different pathophysiologic conditions. All the patients underwent craniotomy, excision of the cyst walls and perforation into the basal cisterns. There was one postoperative death (mortality rate of 1.3%) due to meningitis. The remaining clinical results were gratifying in all three types of lesion; on follow-up CT scans the cysts of type I. and II. exhibited a steady tendency to reduction or obliteration while cerebral reexpansion seemed less evident in the third, most severe, type. The authors compare and discuss the options of radical open surgery versus shunting procedures.

Adolescent↗

Preservation of facial nerve function in acoustic neuroma surgery by the extended middle cranial fossa approach.

The anatomical preservation rates of the facial nerve and postoperative facial nerve function were investigated in cases of initial operation for acoustic neuroma by the middle cranial fossa or extended middle cranial fossa approach. The cases were divided chronologically into three groups according to the date of surgery. The rate of anatomical preservation was 93% in the most recent period, compared to 82.4% for the entire series. This was attributable to higher preservation rates being achieved in cases with medium or large tumors with increased experience. Also regarding postoperative facial nerve function, the number of cases with no paralysis or only partial paralysis increased and the number of cases requiring sacrifice of the facial nerve decreased as experience was accumulated in the series. Even when the facial nerve was preserved anatomically, however, facial-hypoglossal anastomosis was carried out actively if facial nerve function did not recover satisfactorily one year after surgery. For this reason, as many as 33% of the patients underwent anastomosis. This high percentage, however, is attributable to anastomosis ultimately being carried out in 47.7% of the patients in the early period; 22.2% of the patients in the most recent period underwent anastomosis.

Adolescent↗

Dehiscence of the bony roof of the superior semicircular canal in the middle cranial fossa.

Spontaneous dehiscence of the superior semicircular canal (SSC) in the middle cranial fossa is rare and may cause clinical problems. This dehiscence was investigated in cadaveric and dried temporal bone specimens. One cadaveric specimen showed a spontaneous defect: the dehiscence was a symmetrical, elongated ellipse with smooth margins. Four of 244 dry bone specimens showed bony defects in the roof of the SSC, however, only one specimen was thought to have a spontaneous defect. Based on computer-simulation models, we hypothesized that spontaneous defects of the SSC may arise during the fetal period. Although rare, this defect may cause problems in middle cranial fossa surgery and may relate to certain vertiginous disorders.

Aged↗

Image-guided localization of the internal auditory canal via the middle cranial fossa approach.

OBJECTIVE: We sought to determine the accuracy of an electromagnetic image guidance surgical navigation system in localizing the midpoint of the internal auditory canal (IAC) and other structures of the temporal bone through the middle cranial fossa approach. MATERIALS AND METHODS: Seven fresh cadaveric whole heads were dissected via a middle cranial fossa approach. High-resolution CT scans were used with an InstaTrak 3500 Plus electromagnetic image guidance system (General Electric, Fairfield, CT). We evaluated the accuracy of identifying several middle cranial fossa landmarks including the midpoint of the IAC; the labyrinthine segment of the facial nerve; and the arcuate eminence, the carotid artery, and foramen spinosum. RESULTS: We were able to identify the middle of the IAC within 2.31 mm (range 0.65-7.52 mm, SD 2.39 mm). The arcuate eminence could be identified within 1.86 mm (range 1.49-2.37 mm, SD 0.36 mm). We noted some interference when the handpiece was within 6 to 8 cm of the microscope. CONCLUSION: Although computer-aided navigational tools are no substitute for thorough knowledge of temporal bone anatomy, we found the InstaTrak system reliable in identifying the midpoint of the IAC to within 2.4 mm through a middle fossa approach.

Cadaver↗

A new method to identify the internal auditory canal during the middle cranial fossa approach: a preliminary report.

A new method which facilitates identification of the internal auditory canal during the middle cranial fossa approach is described. This method uses illumination of the external auditory meatus as a guide to the internal auditory canal. When the external auditory meatus is illuminated by a light source system such that used for a flexible fiberscope, areas of the middle ear air cell system are illuminated and observable through the plate of bone constituting the base of the middle cranial fossa. In the case of ordinary pneumatization of the middle ear system, the attic is the site of the most intense illumination. Knowledge of the exact location of the attic obtained by this new method is extremely useful when performing drilling to expose the internal auditory canal in the middle cranial fossa approach. This is because the internal auditory canal is located medial to the attic, and also because such knowledge is helpful in identifying the two conventional landmarks of this approach, i.e., the arcuate eminence and the greater superficial petrosal nerve, as the locations of these structures are intimately related to the attic. The method described is very simple, timesaving and inexpensive, and is very helpful in detecting the internal auditory canal. Further anatomical study is being undertaken to establish a method of pinpointing the internal auditory canal, starting from the attic which is readily identifiable by use of this method.

Ear, Inner↗

Surgical anatomy for the extended middle cranial fossa approach.

The surgical anatomy of the temporal bone and the cerebellopontine angle was studied in cadavers, by performing simulated surgery via the extended middle cranial fossa approach. This approach is classified into 3 types according to extension of the drilling area of the temporal bone. In this paper, the surgical anatomy visualized by the EMCF type II and type III is described. In the EMCF type II, mastoidectomy and labyrinthectomy are performed completely through the middle cranial fossa, and in the EMCF type III permitting hearing preservation surgery, sections of the middle cranial fossa dura and the cerebellar tentorium are added to House's middle cranial fossa approach. The comprehension of these anatomical structures is essential for surgeons in performing acoustic neuroma surgery. We believe that this study will serve to expand our knowledge of surgical anatomy, and that as a result the EMCF approach for acoustic neuroma surgery will become more popular.

Cerebellopontine Angle↗

Extended middle cranial fossa approach for acoustic neuroma surgery.

The enlarged middle cranial fossa approach was used for removal of acoustic neuromas in 209 cases. Complete tumor removal was accomplished in 96% of cases. Hearing was preserved in 51% of cases, with better results in smaller tumors. Our experience with the enlarged middle fossa approach has led us to discard the translabyrinthine approach for removal of acoustic neuromas.

Journal Article↗