Microanatomical variations in the cerebellopontine angle associated with vestibular schwannomas (acoustic neuromas): a retrospective study of 1006 consecutive cases

2000 ◽  
Vol 92 (1) ◽  
pp. 70-78 ◽  
Author(s):  
Prakash Sampath ◽  
David Rini ◽  
Donlin M. Long
Keyword(s):  
Cranial Nerve ◽  
Anatomical Location ◽  
Eighth Cranial Nerve ◽  
Content Type ◽  
Middle Fossa Approach ◽  
Group Iii ◽  
Common Location ◽  
Group I ◽  
Cerebellar Artery ◽  
Fine Print

Object. Great advances in neuroimaging, intraoperative cranial nerve monitoring, and microsurgical technique have shifted the focus of acoustic neuroma surgery from prolonging life to preserving cranial nerve function in patients. An appreciation of the vascular and cranial nerve microanatomy and the intimate relationship between neurovascular structures and the tumor is essential to achieve optimum results. In this paper the authors analyze the microanatomical variations in location of the facial and cochlear nerves in the cerebellopontine angle (CPA) associated with acoustic neuromas and, additionally, describe the frequency of involvement of surrounding neural and vascular structures with acoustic tumors of varying size. The authors base these findings on their experience with 1006 consecutive patients who underwent surgery via a retrosigmoid or translabyrinthine approach.Methods. Between July 1969 and January 1998, the senior author (D.M.L.) performed surgery in 1022 patients for acoustic neuroma: 705 (69%) via the retrosigmoid (suboccipital); 301 (29%) via the translabyrinthine; and 16 (2%) via the middle fossa approach. Patients undergoing the middle fossa approach were excluded from the study. The remaining 1006 patients were subdivided into three groups based on tumor size: Group I tumors (609 patients [61%]) were smaller than 2.5 cm; Group II tumors (244 patients [24%]) were between 2.5 and 4 cm; and Group III tumors (153 patients [15%]) were larger than 4 cm. The senior author's operative notes were analyzed for each patient. Relevant cranial nerve and vascular “involvement” as well as anatomical location with respect to the tumor in the CPA were noted. “Involvement” was defined as adherence between neurovascular structure and tumor (or capsule), for which surgical dissection was required to free the structure. Seventh and eighth cranial nerve involvement was divided into anterior, posterior, and polar (around the upper or lower pole) locations. Anterior and posterior locations were further subdivided into upper, middle, or lower thirds of the tumor.The most common location of the seventh cranial nerve (facial) was the anterior middle third of the tumor for all groups, although a significant number were found on the anterior superior portion. The posterior location was exceedingly rare (< 1%). Interestingly, patients with smaller tumors (Group I) had an incidence (3.4%) of the seventh cranial nerve passing through the tumor itself, equal to that of patients with larger tumors. The most common location of the eighth cranial nerve complex was the anterior inferior portion of the tumor. Not surprisingly, larger tumors (Group III) had a higher incidence of involvement of fourth cranial nerve (41%), fifth cranial nerve (100%), ninth—11th cranial nerve complex (99%), and 12th cranial nerve (31%), as well as superior cerebellar artery (79%), anterior inferior cerebellar artery (AICA) trunk (91.5%), AICA branches (100%), posterior inferior cerebellar artery (PICA) trunk (59.5%), PICA branches (79%), and the vertebral artery (VA) (93.5%). A small number of patients in Group III also had AICA (3.3%), PICA (3.3%), or VA (1.3%) vessels within the tumor itself.Conclusions. In this study, the authors show the great variation in anatomical location and involvement of neurovascular structures in the CPA. With this knowledge, they present certain technical lessons that may be useful in preserving nerve function during surgery and, in doing so, hope to provide neurosurgeons and neurootologists with valuable information that may help to achieve optimum outcomes in patients.

Microanatomical variations in the cerebellopontine angle associated with vestibular schwannomas (acoustic neuromas)

1998 ◽  
Vol 5 (3) ◽  
pp. E3
Author(s):  
Prakash Sampath ◽  
David Rini ◽  
Donlin M. Long
Keyword(s):  
Cranial Nerve ◽  
Anatomical Location ◽  
Middle Fossa Approach ◽  
Seventh Cranial Nerve ◽  
Acoustic Neuromas ◽  
Common Location ◽  
Cerebellar Artery ◽  
Group 3 ◽  
Neurovascular Structures ◽  
Group 1

Great advances in neuroimaging, intraoperative cranial nerve monitoring, and microsurgical technique have shifted the focus of acoustic neuroma surgery from prolonging life to preserving cranial nerve function in patients. An appreciation of the vascular and cranial nerve microanatomy and the intimate relationship between neurovascular structures and the tumor is essential to achieve optimum results. In this paper the authors analyze the microanatomical variations in location of the facial and cochlear nerves in the cerebellopontine angle (CPA) associated with acoustic neuromas and, additionally, describe the frequency of involvement of surrounding neural and vascular structures with acoustic tumors of varying size. The authors base their findings on their experience treating 1006 consecutive patients who underwent surgery via a retrosigmoid or translabyrinthine approach. Between July 1969 and January 1998, the senior author (D.M.L.) performed surgery in 1022 patients for acoustic neuroma: 705 (69%) via the retrosigmoid (suboccipital); 301 (29%) via translabyrinthine; and 16 (2%) via middle fossa approach. Patients undergoing the middle fossa approach were excluded from the study. Patients were subdivided into three groups based on tumor size: Group 1 tumors (609 patients [61%]) were smaller than 2.5 cm; Group 2 tumors (244 patients [24%]) were between 2.5 and 4 cm; and Group 3 tumors (153 patients [15%]) were larger than 4 cm. Operative notes were analyzed for each patient. Relevant cranial nerve and vascular “involvement” as well as anatomical location with respect to the tumor in the CPA were noted. “Involvement” was defined as intimate contact between neurovascular structure and tumor (or capsule), where surgical dissection was required to free the structure. Seventh and eighth cranial nerve involvement was divided into anterior, posterior, and polar (around the upper or lower pole) locations. Anterior and posterior locations were further subdivided into upper, middle, or lower thirds of the tumor. The most common location of the seventh cranial nerve (facial) was the anterior middle third of the tumor for Groups 1, 2, and 3, although a significant number were found on the anterior superior portion. The posterior location was exceedingly rare (< 1%). Interestingly, patients with smaller tumors (Group 1) had an incidence (3.4%) of the seventh cranial nerve passing through the tumor itself equal to that of patients with larger tumors. The most common location of the seventh cranial nerve complex was the anterior inferior portion of the tumor. Not surprisingly, larger tumors (Group 3) had a higher incidence of involvement of sixth cranial nerve (41%), fifth cranial nerve (100%), ninth-11th cranial nerve complex (99%), 12th cranial nerve (31%), as well as superior cerebellar artery (79%), anterior inferior cerebellar artery (AICA) trunk (91.5%), AICA branches (100%), posterior inferior cerebellar artery (PICA) trunk (59.5%), PICA branches (79%), and the vertebral artery (93.5%). A small number of patients in Group 3 also had AICA (3.3%), PICA (3.3%), or vertebral artery (1.3%) vessels within the tumor itself. In this study, the authors show the great variation in anatomical location and involvement of neurovascular structures in the CPA. With this knowledge, they present certain technical lessons that may be useful in preserving function during surgery and, in doing so, hope to provide neurosurgeons and neurootologists with valuable information that may help to achieve optimum cranial nerve outcomes in patients.

Effect of initially limited resuscitation in a combined model of fluid-percussion brain injury and severe uncontrolled hemorrhagic shock

2000 ◽  
Vol 93 (2) ◽  
pp. 305-314 ◽  
Author(s):  
Susan A. Stern ◽  
Brian J. Zink ◽  
Michelle Mertz ◽  
Xu Wang ◽  
Steven C. Dronen
Keyword(s):  
Brain Injury ◽  
Physiological Parameters ◽  
Content Type ◽  
Group Iii ◽  
Fluid Percussion ◽  
Group I ◽  
Group Ii ◽  
Goal Map ◽  
Uncontrolled Hemorrhage ◽  
Fine Print

Object. Studies of isolated uncontrolled hemorrhage have indicated that initial limited resuscitation improves survival. Limited resuscitation has not been studied in combined traumatic brain injury and uncontrolled hemorrhage. In this study the authors evaluated the effects of limited resuscitation on outcome in combined fluid-percussion injury (FPI) and uncontrolled hemorrhage.Methods. Twenty-four swine weighing 17 to 24 kg each underwent FPI (3 atm) and hemorrhage to a mean arterial pressure (MAP) of 30 mm Hg in the presence of a 4-mm aortic tear. Group I (nine animals) was initially resuscitated to a goal MAP of 60 mm Hg; Group II (nine animals) was resuscitated to a goal MAP of 80 mm Hg; and Group III (control; six animals) was not resuscitated. After 60 minutes, the aortic hemorrhage was controlled and the animals were resuscitated to baseline physiological parameters and observed for 150 minutes.Mortality rates were 11%, 50%, and 100% for Groups I, II, and III, respectively (Fisher's exact test; p = 0.002). The total hemorrhage volume was greater in Group II (69 ± 32 ml/kg), as compared with Group I (41 ± 18 ml/kg) and Group III (37 ± 3 ml/kg) according to analysis of variance (p < 0.05). In surviving animals, cerebral perfusion pressure, cerebral blood flow (CBF), cerebral venous O2 saturation (ScvO2), and cerebral metabolic rate of O2 did not differ among groups. Although CBF was approximately 50% of baseline during the period of limited resuscitation in Group I, ScvO2 remained greater than 60%, and arteriovenous O2 differences remained within normal limits.Conclusions. In this model of FPI and uncontrolled hemorrhage, early aggressive resuscitation, which is currently recommended, resulted in increased hemorrhage and failure to optimize cerebrovascular parameters. In addition, a 60-minute period of moderate hypotension (MAP = 60 mm Hg) was well tolerated and did not compromise cerebrovascular hemodynamics, as evidenced by physiological parameters that remained within the limits of cerebral autoregulation.

Expression of matrix metalloproteinases 2 and 9 in meningiomas associated with different degrees of brain invasiveness and edema

2001 ◽  
Vol 95 (5) ◽  
pp. 839-844 ◽  
Author(s):  
Ann-Christin Sandberg Nordqvist ◽  
Hubert Smurawa ◽  
Tiit Mathiesen
Keyword(s):  
Matrix Metalloproteinases ◽  
Clear Correlation ◽  
Consecutive Series ◽  
Tissue Samples ◽  
Content Type ◽  
Brain Invasion ◽  
Group Iii ◽  
Tumor Invasiveness ◽  
Group I ◽  
Fine Print

Object. Meningiomas display clinical characteristics that vary from very benign to clearly malignant with rapid invasive growth and metastasis. Benign meningiomas differ in their invasiveness and concomitant edema. This study was undertaken to analyze the expression of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9, respectively) in meningiomas associated with different degrees of brain invasion and edema. Methods. Tissue samples from 16 meningiomas were selected according to tumor invasiveness from a consecutive series of patients. Samples were analyzed for expression of both MMP-2 and MMP-9 by using in situ hybridization. The meningiomas consisted of three types: Group I, benign meningiomas that did not interfere with the arachnoid plane and exhibited no edema; Group II, benign meningiomas that invaded the arachnoid plane and caused edema; and Group III, aggressive and malignant meningiomas that caused edema and displayed brain invasion. In all 16 tumors analyzed, MMP-2 mRNA was identified. Levels of expression of MMP-2 mRNA were similar in all samples, and no correlation with increasing tumor invasiveness or associated edema could be detected. Expression of MMP-9 mRNA was identified in 14 of the 16 tumors, and a clear correlation with increasing tumor invasion into the brain was noted. Conclusions. Meningiomas express both MMP-2 and MMP-9. Tumor invasiveness, which ranged from minor with respect to the arachnoid membrane and progressed to frank brain invasion, correlated with the extent of MMP-9 expression. The findings indicate that MMP-9 expression and brain invasion are relevant mechanisms that must be interfered with in the treatment of aggressive and malignant meningiomas. No such correlation with MMP-2 was found.

Clinoidal meningiomas

1990 ◽  
Vol 73 (6) ◽  
pp. 840-849 ◽  
Author(s):  
Ossama Al-Mefty
Keyword(s):  
Cerebral Vessels ◽  
Sinus Surgery ◽  
Morbidity Rate ◽  
Total Removal ◽  
Content Type ◽  
Mortality And Morbidity ◽  
Group Iii ◽  
Group I ◽  
Subtotal Removal ◽  
Fine Print

✓ Anterior clinoidal meningiomas are frequently grouped with suprasellar or sphenoid ridge meningiomas, masking their notorious association with a high mortality and morbidity rate, failure of total removal, and recurrence. To avoid injury to encased cerebral vessels, most surgeons are content with subtotal removal. Without total removal, however, recurrence is expected. Recent advances in cranial-base exposure and cavernous sinus surgery have facilitated radical total removal. The author reports 24 cases operated on with vigorous attempts at total removal of the tumor with involved dura and bone. This experience has distinguished three groups (I, II, and III) which influence surgical difficulties, the success of total removal, and outcome. These subgroups relate to the presence of interfacing arachnoid membranes between the tumor and cerebral vessels. The presence or absence of arachnoid membranes depends on the origin of the tumor and its relation to the naked segment of carotid artery lying outside the carotid cistern. Total removal was impossible in the three patients in Group I, with postoperative death occurring in one patient and hemiplegia in another. Total removal was achieved in 18 of the 19 patients in Group II, with one death from pulmonary embolism. In the two patients in Group III, total removal without complications was easily achieved.

Duraplasty with biosynthetic cellulose: an experimental study

1997 ◽  
Vol 86 (1) ◽  
pp. 143-150 ◽  
Author(s):  
Luis Renato Mello ◽  
Leonir T. Feltrin ◽  
Paulo T. Fontes Neto ◽  
Fernando A. P. Ferraz
Keyword(s):  
Dura Mater ◽  
Clinical Symptoms ◽  
Early Postoperative Period ◽  
Cellulose Membrane ◽  
Content Type ◽  
Group Iii ◽  
Temporal Fascia ◽  
Group I ◽  
Fine Print

✓ In the search for a new synthetic substitute for the dura mater, the authors conducted a research study using 32 mongrel dogs divided into three groups. Group I animals (21 dogs) underwent a right-sided parietooccipital craniotomy and substitution of two 1-cm pieces of dura mater by two different grafts: one piece of biosynthetic cellulose (50 µ thick) and one fragment of temporal fascia. The animals were observed for 30, 90, or 180 days. Group II animals (five dogs) underwent a somewhat larger craniotomy, removal of a 2-cm piece of dura mater, and lesioning of the cortex made by a thin sharp forceps, which caused bleeding that was controlled by application of a thin film of cellulose (10 µ thick). Duraplasty was performed using a 50-µ-thick cellulose membrane to complete the procedure and the animals were observed over a period of 270 days. Group III animals (six dogs) underwent smaller (1-cm diameter) bilateral parietal craniectomy, which included additional covering of the dura on the left side with 50-µ-thick cellulose and a suture of temporalis muscle. This group was observed for 40, 60, 80, or 120 days. Transient mild clinical symptoms were observed during the early postoperative period. At autopsy, macroscopic examination demonstrated good acceptance of the grafts with few and moderate extradural fibrosis, which caused adherence of the implants to the bone fragment. No adherence to the cortex was observed. Microscopic examination demonstrated absence of graft adherence to the cortical surface even when the cortex was injured. The cellulose was enveloped by two layers of connective tissue, the external layer being thicker than the internal one. Cellulose fibers increased in thickness over time until 30 days and then decreased in thickness until 270 days. This decrease in thickness between 30 to 270 days was statistically significant (p < 0.05). The physical properties of biosynthetic cellulose and the low cellular reaction to its implantation qualify this material as a dural substitute. Additional long-term studies must be undertaken to complete this report.

Microvascular decompression for cochlear symptoms

2000 ◽  
Vol 93 (3) ◽  
pp. 421-426 ◽  
Author(s):  
Tomomi Okamura ◽  
Yasushi Kurokawa ◽  
Norio Ikeda ◽  
Seisho Abiko ◽  
Makoto Ideguchi ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Microvascular Decompression ◽  
Cranial Nerve ◽  
Cochlear Nerve ◽  
Auditory Brainstem Responses ◽  
Neurovascular Compression ◽  
Minimal Risk ◽  
Eighth Cranial Nerve ◽  
Content Type ◽  
Fine Print

Object. The object of this study was to evaluate the efficacy of a new neurovascular decompression technique in relieving symptoms of cochlear nerve dysfunction.Methods. Nineteen patients with slowly progressive hearing loss, low-frequency fluctuating hearing loss, and high-pitched tinnitus due to neurovascular compression (NVC) of the eighth cranial nerve in a triangular space between the seventh and eighth cranial nerves (the VII–VIII triangle) of the cerebellopontine angle (CPA) were treated using a new technique for microvascular decompression that was developed by anatomical study in 24 cadaver specimens of the CPA. In 12 of 19 patients the anterior inferior cerebellar artery (AICA) was observed to cause compression in the VII–VIII triangle and this vessel was easily mobilized medially for placement of a silicone sponge or Teflon cushion between the compressing artery and nerve. Postoperatively, hearing loss of 20 dB or more that was present in 11 of the 19 patients with NVC improved by more than 5 dB in seven (64%), including the patient with the most severe hearing loss. Of 18 patients presenting with tinnitus preoperatively, eight (44%) had no tinnitus and an additional nine (for a total of 94%) had good improvement in tinnitus after surgery and at long-term follow up.Conclusions. The microvascular decompression technique described is highly successful in treating symptoms due to direct or indirect compression of the cochlear nerve, with minimal risk of complications. Recordings of auditory brainstem responses confirmed the clinical diagnosis of NVC of the eighth cranial nerve and correlated with clinical results after microvascular decompression of the cochlear nerve.

Evaluation of the healing process after dural reconstruction achieved using a free fascial graft

2002 ◽  
Vol 96 (2) ◽  
pp. 280-286 ◽  
Author(s):  
Eiji Tachibana ◽  
Kiyoshi Saito ◽  
Keizo Fukuta ◽  
Jun Yoshida
Keyword(s):  
Growth Factor ◽  
Subcutaneous Tissue ◽  
Healing Process ◽  
Fibrous Tissue ◽  
Dural Repair ◽  
Content Type ◽  
Group Iii ◽  
Group I ◽  
Silicone Sheet ◽  
Fine Print

Object. This study was undertaken to investigate the healing process and to delineate factors important for the survival of free fascial grafts used for dural repair. Methods. A dural defect was created in guinea pigs and then reconstructed using either a free fascial graft or an expanded polytetrafluoroethylene (ePTFE) sheet. The fascial graft was covered directly by subcutaneous tissue (Group I) or by a silicone sheet to prevent tissue ingrowth from the subcutaneous tissue (Group II). The ePTFE sheet was covered with a silicone sheet (Group III). One or 2 weeks postoperatively, the strength of the dural repair was evaluated by determining the pressure at which cerebrospinal fluid (CSF) leaked through the wound margins. The dural repair was also histologically examined. In addition, using a rat model, specimens obtained from similar reconstruction sites were immunohistochemically stained with antibodies against basic fibroblast growth factor (bFGF), epidermal growth factor, or transforming growth factor—β. The pressures at which CSF leaked after 1 and 2 weeks, respectively, were 50 ± 14 mm Hg and 126 ± 20 mm Hg in Group I, 70 ± 16 mm Hg and 101 ± 38 mm Hg in Group II, and 0 mm Hg and 8 ± 8 mm Hg in Group III. Failure of repairs made in Group III occurred at significantly lower pressures when compared with Groups I and II. In Groups I and II, a thick fibrous tissue formed around the fascial graft. This tissue tightly adhered to adjacent dura mater. The fibrous tissue displayed a positive reaction for the presence of bFGF. In Group III, only a thin fibrous membrane surrounded the ePTFE sheet. Conclusions. Fascial grafts tolerated extraordinary intracranial pressures at 1 week postoperatively. Free fascial grafts can heal with durable fibrous tissue without the presence of a blood supply from an overlying vascularized flap.

Trigeminal schwannomas: removal of dumbbell-shaped tumors through the expanded Meckel cave and outcomes of cranial nerve function

2002 ◽  
Vol 96 (3) ◽  
pp. 453-463 ◽  
Author(s):  
Ossama Al-Mefty ◽  
Samer Ayoubi ◽  
Esam Gaber
Keyword(s):  
Cranial Nerve ◽  
Nerve Function ◽  
Middle Fossa ◽  
Total Removal ◽  
Content Type ◽  
Middle Fossa Approach ◽  
Cranial Nerve Function ◽  
Nerve Paresis ◽  
Abducent Nerve ◽  
Fine Print

Object. As in patients with vestibular schwannomas, advances in surgical procedures have markedly improved outcomes in patients with trigeminal schwannomas. In this article the authors address the function of cranial nerves in a series of patients with trigeminal schwannomas that were treated with gross-total surgical removal. The authors emphasize a technique they use to remove a dumbbell-shaped tumor through the expanded Meckel cave, and discuss the advantage of the extradural zygomatic middle fossa approach for total removal of tumor and preservation or improvement of cranial nerve function. Methods. Within an 11-year period (1989–2000), 25 patients (14 female and 11 male patients with a mean age of 44.4 years) with benign trigeminal schwannomas were surgically treated by the senior author (O.A.) with the aim of total removal of the tumor. Three patients had undergone previous surgery elsewhere. Trigeminal nerve dysfunction was present in all but two patients. Abducent nerve paresis was present in 40%. The approach in each patient was selected according to the location and size of the lesion. Nineteen tumors were dumbbell shaped and extended into both middle and posterior fossae. All 25 tumors involved the cavernous sinus. The zygomatic middle fossa approach was particularly useful and was used in 14 patients. The mean follow-up period was 33.12 months. In patients who had not undergone previous surgery, the preoperative trigeminal sensory deficit improved in 44%, facial pain decreased in 73%, and trigeminal motor deficit improved in 80%. Among patients with preoperative abducent nerve paresis, recovery was attained in 63%. Three patients (12%) experienced a persistent new or worse cranial nerve function postoperatively. Fifth nerve sensory deficit persisted in one of these patients, sensory and motor dysfunction in another, and motor trigeminal weakness in the third patient. In all patients a good surgical outcome was achieved. One patient died 2 years after treatment from an unrelated cause. In three patients the tumors recurred after an average of 22.3 months. Conclusions. Preservation or improvement of cranial nerve function can be achieved through total removal of a trigeminal schwannoma, and skull base approaches are better suited to achieving this goal. The zygomatic middle fossa approach is particularly helpful and safe. It allows extradural tumor removal from the cavernous sinus, the infratemporal fossa, and the posterior fossa through the expanded Meckel cave.

Role of estrogen deficiency in the formation and progression of cerebral aneurysms. Part I: experimental study of the effect of oophorectomy in rats

2005 ◽  
Vol 103 (6) ◽  
pp. 1046-1051 ◽  
Author(s):  
Mohammad A. Jamous ◽  
Shinji Nagahiro ◽  
Keiko T. Kitazato ◽  
Junichiro Satomi ◽  
Koichi Satoh
Keyword(s):  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Bilateral Oophorectomy ◽  
Gelatinase Activity ◽  
Content Type ◽  
Group Iii ◽  
Group I ◽  
Group Ii ◽  
Fine Print

Object. Estrogen has been shown to play a central role in vascular biology. Although it may exert beneficial vascular effects, its role in the pathogenesis of cerebral aneurysms remains to be determined. To elucidate the role of hormones further, the authors examined the effects of bilateral oophorectomy on the formation and progression of cerebral aneurysms in rats. Methods. Forty-five female, 7-week-old Sprague—Dawley rats were divided into three equal groups. Group I consisted of intact rats (controls). To induce cerebral aneurysms, the animals in Groups II and III were subjected to ligation of the right common carotid and bilateral posterior renal arteries. One month later, the rats in Group II underwent bilateral oophorectomy. Three months after the experiment began all animals were killed and cerebral vascular corrosion casts were prepared and screened for cerebral aneurysms by using a scanning electron microscope. Plasma was used to determine the level of estradiol and the gelatinase activity. Hypertension developed in all rats except those in the control group. The estradiol level was significantly lower in Group II than in the other groups (p < 0.01). The incidence of cerebral aneurysm formation in Group II (60%) was three times higher than that in Group III (20%), and the mean size of aneurysms in Group II (76 ± 27 µm, mean ± standard deviation) was larger than that in Group III (28 ± 4.6 µm) (p < 0.05). No aneurysm developed in control animals (Group I), and there was no significant difference in plasma gelatinase activity among the three groups. Conclusions. The cerebral aneurysm model was highly reproducible in rats. Bilateral oophorectomy increased the susceptibility of rats to aneurysm formation, indicating that hormones play a role in the pathogenesis of cerebral aneurysms.

Neurovascular decompression of the eighth cranial nerve in patients with hemifacial spasm and incidental tinnitus: an alternative way to study tinnitus

1998 ◽  
Vol 88 (2) ◽  
pp. 232-236 ◽  
Author(s):  
Hiroshi Ryu ◽  
Seiji Yamamoto ◽  
Kenji Sugiyama ◽  
Kenichi Uemura ◽  
Michihiko Nozue
Keyword(s):  
Hemifacial Spasm ◽  
Cranial Nerve ◽  
Diagnostic Value ◽  
Sensorineural Hearing ◽  
Neurovascular Compression ◽  
Eighth Cranial Nerve ◽  
Chi Square ◽  
Content Type ◽  
Neurovascular Decompression ◽  
Fine Print

Object. The authors sought to clarify the clinical characteristics of tinnitus resulting from neurovascular compression (NVC) of the eighth cranial nerve. Methods. The authors explored the eighth cranial nerve in the cerebellopontine cistern during neurovascular decompression (NVD) of the facial nerve in 10 patients with hemifacial spasm who suffered from incidental tinnitus on the same side. The diagnosis of NVC of the eighth cranial nerve was confirmed in all patients. This condition was found in only seven of 114 patients with hemifacial spasm alone, indicating that NVC of the eighth cranial nerve is one of the causes of tinnitus (p < 0.001, chi-square test). The tinnitus resolved or was markedly improved after NVD of the eighth cranial nerve in eight patients (80%). Both pulsatile and continuous tinnitus responded well to NVD. All patients experienced various degrees of sensorineural hearing disturbance, but other neurotological examinations provided poor diagnostic value. Conclusions. It is the authors' opinion that sensorineural hearing loss and positive findings on magnetic resonance imaging are the most reliable evidence for the presence of tinnitus caused by NVC of the eighth cranial nerve.

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