Hemifacial spasm: three-dimensional MR images in the evaluation of neurovascular compression

Acquired onset of third, fourth, and sixth cranial nerve palsies in children and adolescents

PURPOSE

To describe the causes of third, fourth, and sixth cranial nerve palsies in children and adolescents.

METHODS

In this retrospective case series, a total of 66 patients aged 0-19 years with third, fourth, and sixth cranial nerve palsies seen in strabismus and neuro-ophthalmic practice from 2010 to 2017 were included. Causes of palsies were determined based on clinical assessment, high-resolution magnetic resonance imaging (MRI), and laboratory work-up.

RESULTS

Thirty-five patients had sixth cranial nerve palsy, 14 patients had third cranial nerve palsy (7 partial, 7 complete), 13 patients had fourth cranial nerve palsy, and 4 patients had combined cranial nerve palsies in this study. Neoplasia involving central nervous system was one of the most common causes of third, fourth, and sixth cranial nerve palsies both in children (age: 0-14 years) and adolescents (age: 15-19 years) (20% and 31%, respectively). Overall, neoplasia (23%) was the most common cause of acute third, fourth, and sixth cranial nerve palsies, followed by idiopathic cause (14%), inflammation (11%), and non-aneurysmal vascular contact (11%). Neoplasia was also the most common cause of sixth and third cranial nerve palsies (25% and 29%, respectively). The most common cause of fourth cranial nerve palsy was late decompensation in congenital fourth cranial nerve palsy (46%).

CONCLUSIONS

A substantial proportion of pediatric and juvenile patients had serious pathologies for third, fourth, and sixth cranial nerve palsies. If nerve palsies are indicated, prompt diagnosis of etiologies using high-resolution MRI with contrast and laboratory work-up are important for this disease population.

Comparison of brain MRI angiography and brain MRI cisternography in patients with hemifacial spasm

OBJECTIVE

The aim of this study was to compare the ability of brain magnetic resonance imaging angiography and brain magnetic resonance imaging cisternography of showing the neurovascular contiguity of the facial nerve in patients with hemifacial spasm.

METHOD

This study included a total of 35 patients (28 females, 7 males), with an average age of 57.5 ± 13.8 years, who presented to our outpatient clinic of movement disorders. All patients were prospectively applied brain magnetic resonance imaging angiography and brain magnetic resonance imaging cisternography, and the results were evaluated by a radiologist who was blind to study protocol.

RESULTS

The study included 35 patients, of whom 28 (80 %) were female and 7 (20 %) were male. Brain magnetic resonance imaging angiography demonstrated facial nerve compression of vascular origin in 5 (14.3 %) patients presenting with the clinical presentation of hemifacial spasm. Neurovascular compression of facial nerve was shown by brain magnetic resonance imaging cisternography in 13 (37.1 %) patients.

CONCLUSION

No statistically significant difference was found between brain magnetic resonance imaging angiography and brain magnetic resonance imaging cisternography techniques in detecting a compressive interaction causing hemifacial spasm between facial nerve and adjacent vascular structures (p > 0.05).

High-resolution STIR for 3-T MRI of the posterior fossa: visualization of the lower cranial nerves and arteriovenous structures related to neurovascular compression

OBJECTIVE

Preoperative evaluation of small vessels without contrast material is sometimes difficult in patients with neurovascular compression disease. The purpose of this retrospective study was to evaluate whether 3D STIR MRI could simultaneously depict the lower cranial nerves--fifth through twelfth--and the blood vessels in the posterior fossa.

MATERIALS AND METHODS

The posterior fossae of 47 adults (26 women, 21 men) without gross pathologic changes were imaged with 3D STIR and turbo spin-echo heavily T2-weighted MRI sequences and with contrast-enhanced turbo field-echo MR angiography (MRA). Visualization of the cranial nerves on STIR images was graded on a 4-point scale and compared with visualization on T2-weighted images. Visualization of the arteries on STIR images was evaluated according to the segments in each artery and compared with that on MRA images. Visualization of the veins on STIR images was also compared with that on MRA images. Statistical analysis was performed with the Mann-Whitney U test.

RESULTS

There were no significant differences between STIR and T2-weighted images with respect to visualization of the cranial nerves (p > 0.05). Identified on STIR and MRA images were 94 superior cerebellar arteries, 81 anteroinferior cerebellar arteries, and 79 posteroinferior cerebellar arteries. All veins evaluated were seen on STIR and MRA images. There were no significant differences between STIR and MRA images with respect to visualization of arteries and veins (p > 0.05).

CONCLUSION

High-resolution STIR is a feasible method for simultaneous evaluation of the lower cranial nerves and the vessels in the posterior fossa without the use of contrast material.

Can 3T MR angiography replace DSA for the identification of arteries feeding intracranial meningiomas?

BACKGROUND AND PURPOSE

For identifying the arterial feeders of meningiomas, the usefulness of 3D TOF MRA at 3T has not been systematically investigated. This study was intended to assess whether unenhanced 3D TOF MRA at 3T can replace DSA for the identification of arteries feeding intracranial meningiomas and whether it is useful for assessing their dural attachment.

MATERIALS AND METHODS

Twenty-one consecutive patients with intracranial meningiomas (18 women, 3 men; aged 42-77 years, mean 57 years) underwent DSA, conventional MR imaging, and 3D TOF MRA. Two neuroradiologists independently evaluated the primary and secondary feeders of each tumor on maximum-intensity-projection and source MRA images. They also identified the location of dural attachments based on information from MR imaging/MRA images. Interobserver and intermodality agreement was determined by calculating the κ coefficient.

RESULTS

For the identification of primary and secondary feeders on MRA images, interobserver agreement was very good (κ=0.83; 95% CI, 0.66-1.00) and moderate (κ=0.58; 95% CI, 0.34-0.82) and intermodality agreement (consensus reading of MRA versus DSA findings) was excellent (κ=0.94; 95% CI, 0.84-1.00) and good (κ=0.72; 95% CI, 0.51-0.93), respectively. With respect to the dural attachment of meningiomas, interobserver agreement was very good (κ=0.95; 95% CI, 0.84-1.00). The agreement in the diagnosis between MR imaging/MRA and surgery was excellent (κ=1.00).

CONCLUSIONS

Unenhanced 3D TOF MRA at 3T cannot at present supplant DSA for the identification of the feeding arteries of intracranial meningiomas. This information may be useful for evaluating their dural attachment.

Nonaneurysmal cranial nerve compression as cause of neuropathic strabismus: evidence from high-resolution magnetic resonance imaging

PURPOSE

To seek evidence of neurovascular compression of motor cranial nerves (CNs) in otherwise idiopathic neuropathic strabismus using high-resolution magnetic resonance imaging (MRI).

DESIGN

Prospective, observational case series.

METHODS

High-resolution, surface coil orbital MRI was performed in 10 strabismic patients with idiopathic oculomotor (CN III) or abducens (CN VI) palsy. Relationships between CNs and intracranial arteries were demonstrated by 0.8-mm thick, 162-μm resolution, heavily T2-weighted MRI in fast imaging using steady-state acquisition sequences. Images were analyzed digitally to evaluate cross-sectional areas of extraocular muscles.

RESULTS

In one patient with CN III palsy, an ectatic posterior communicating artery markedly flattened and thinned the ipsilateral subarachnoid CN III. Cross-sections of the affected medial, superior, and inferior rectus muscles 10 mm posterior to the globe-optic nerve junction were 17.2 ± 2.5 mm(2), 15.5 ± 1.3 mm(2), and 9.9 ± 0.8 mm(2), significantly smaller than the values of 23.6 ± 1.9 mm(2), 30.4 ± 4.1 mm(2), and 28.8 ± 4.6 mm(2), respectively, of the unaffected side (P < .001). In 2 patients with otherwise unexplained CN VI palsy, ectatic basilar arteries contacted CN VI. Mean cross-sections of affected lateral rectus muscles were 24.0 ± 2.3 mm(2) and 29.8 ± 3.1 mm(2), significantly smaller than the values of 33.5 ± 4.1 mm(2) and 36.9 ± 1.6 mm(2), respectively, in unaffected contralateral eyes (P < .05).

CONCLUSIONS

Nonaneurysmal motor CN compression should be considered as a cause of CN III and CN VI paresis with neurogenic muscle atrophy when MRI demonstrates vascular distortion of the involved CN. Demonstration of a benign vascular cause can terminate continuing diagnostic investigations and can expedite rational management of the strabismus.

Preoperative evaluation of neurovascular relationships for microvascular decompression in the cerebellopontine angle in a virtual reality environment

Object

In this paper the authors' goal was to evaluate the feasibility and efficacy of a virtual reality (VR) system in preoperative planning for microvascular decompression (MVD) procedures treating idiopathic trigeminal neuralgia and hemifacial spasm. The system's role in surgical simulation and training was also assessed.

Methods

Between May 2008 and April 2009, the authors used the Dextroscope system to visualize the neurovascular complex and simulate MVD in the cerebellopontine angle in a VR environment in 16 patients (6 patients had trigeminal neuralgia and 10 had hemifacial spasm). Reconstructions were carried out 2–3 days before MVD. Images were printed in a red-blue stereoscopic format for teaching and discussion and were brought into the operating room to be compared with real-time intraoperative findings.

Results

The VR environment was a powerful aid for spatial understanding of the neurovascular relationship in MVD for operating surgeons and trainees. Through an initial series of comparison/confirmation experiences, the senior neurosurgeon became accustomed to the system. He could predict intraoperative problems and simulate surgical maneuvering, which increased his confidence in performing the procedure.

Conclusions

The Dextroscope system is an easy and rapid method to create a stereoscopic neurovascular model for MVD that is highly concordant with intraoperative findings. It effectively shortens the learning curve and adds to the surgeon's confidence.

Anatomical features of the cisternal segment of the oculomotor nerve: neurovascular relationships and abnormal compression on magnetic resonance imaging

OBJECT

The object of this study was to assess the detailed anatomical features and vascular relationships of the cisternal segment of the oculomotor nerve, and to assess the utility of MR imaging in oculomotor nerve palsy caused by abnormal compression related to arteries and tumors.

METHODS

The anatomy of the oculomotor nerve was depicted using 3D Fourier transformation constructive interference in steady-state (CISS) MR imaging in 196 volunteers (392 total nerves), in 9 patients with paralysis of the oculomotor nerve, and in 1 preoperative patient with cholesteatoma in the pontine cistern. The vessels adjacent to the oculomotor nerve were detected and compared using 3D time-of-flight MR imaging. The 3D CISS multiplanar reconstruction (MPR) images of the oculomotor nerve in cadavers and in specimens from the cadavers were used to verify the oculomotor nerve shown in the 196 patients. The images were assessed with respect to the demonstration of the oculomotor nerve, the optimal display angles on MPR images, the visualized length of the nerve, neurovascular relationships, and abnormal compression caused by arteries and tumors.

RESULTS

Three-dimensional CISS MR imaging depicted the cisternal segment of the oculomotor nerve with certainty in 100% of the patients in the transverse, sagittal, and coronal planes. Three-dimensional CISS imaging of the oculomotor nerve in 196 volunteers revealed similar results corresponding to 3D CISS MPR images of cadavers and cadaver specimens. The maximum visualized length of the oculomotor nerve was 14.61 +/- 2.33 mm. The angle between the oculomotor nerve and the median sagittal plane was 24.48 +/- 4.57 degrees on the left and 24.48 +/- 5.07 degrees on the right. The posterior cerebral artery was observed to contact the oculomotor nerve in 216 (55.1%) of 392 nerves, and the superior cerebellar artery was observed to contact the oculomotor nerve in 231 (58.9%) of 392 nerves. The abnormal nerve compression in 9 patients with paralysis of the oculomotor nerve was displayed well in all patients. The adjacent relationship of the oculomotor nerve in 1 preoperative patient with cholesteatoma in the pontine cistern was also demonstrated clearly.

CONCLUSIONS

Use of 3D CISS sequences and 3D time-of-flight sequences enables accurate identification of the cisternal segment of the oculomotor nerve, neurovascular relationships, and abnormal compression caused by arteries and tumors.

Imaging of the facial nerve

A variety of congenital, traumatic, vascular, inflammatory, and neoplastic processes may affect the facial nerve. Prudent use of CT and MR imaging combined with a complete understanding of facial nerve anatomy helps in narrowing the differential diagnosis. The precise anatomic course of the facial nerve must be charted in patients who undergo middle ear surgery. Also of great importance is recognition of the fact that the facial nerve may be affected in cancers of the head and neck by perineural spread. This article reviews the anatomy of the facial nerve and relevant, current clinical evaluation and imaging strategies.

The superiority of 3D-CISS sequence in displaying the cisternal segment of facial, vestibulocochlear nerves and their abnormal changes

OBJECTIVE

To select the best imaging method for clinical otologic patients through evaluating 3D constructive interference of steady state (CISS) image quality in visualizing the facial, vestibulocochlear nerves (CN:VII-VIII) and their abnormal changes.

METHODS

The CN:VII-VIII as well as inner ear structures in 48 volunteers were examined using 3D-CISS and 3D turbo spin echo (TSE) sequences respectively, and displayed to the full at the reformatted and maximum intensity projection (MIP) images. The nerve identification and image quality were graded for the CN:VII-VIII as well as inner ear structures. Statistical analysis was performed using the Wilcoxin test, p<0.05 was considered significant. In addition, 8 patients with abnormality in facial or vestibulocochlear nerves were also examined using 3D-CISS sequence.

RESULTS

The identification rates for the cisternal segment of facial, vestibulocochlear nerves and corresponding membranous labyrinth were 100%. Abnormal changes of the facial or vestibulocochlear nerves were clearly shown in 8 patients, among them 1 was caused by bilateral acoustic neurinoma, 1 by cholesteatoma at cerebellopontine angle, 1 by arachnoid cyst, 1 by neurovascular adhesion, 4 by neurovascular compression.

CONCLUSION

With 3D-CISS sequence the fine structure of the CN:VII-VIII and corresponding membranous labyrinth can be clearly demonstrated; lesions at the site of cerebellopontine angle can also be found easily.

Microvascular decompression for intractable singultus: technical case report

OBJECTIVE

Intractable singultus is a rare but significantly disruptive clinical phenomenon that often accompanies other diseases but can present in isolation due entirely to intracranial pathology. We report a case of intractable singultus that improved after microvascular decompression and present a comprehensive review of singultus by discussing its similarity to other cases of microvascular decompression, its history and etiology, and its evolutionary basis.

CLINICAL PRESENTATION

The patient exhibited intractable singultus for 15 years, resistant to multiple medical regimens.

INTERVENTION

Microvascular decompression to relieve pressure on the tenth cranial nerve and medulla oblongata resulted in near total resolution of the singultus.

CONCLUSION

Neurovascular compression should be considered a potentially reversible cause of intractable singultus, a significantly disabling clinical phenomenon.

Depiction of the cranial nerves within the brain stem with use of PROPELLER multishot diffusion-weighted imaging

Despite the recent progress of MR imaging, visualization of the cranial nerves within the brain stem has not been accomplished. Periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) multishot diffusion-weighted imaging, an effective method for compensating for motion and distortion, offers high-quality diffusion-weighted images. We succeeded in depicting the cranial nerves within the brain stem in some subjects by using this method with motion-probing gradient applied in the superior-inferior direction.

A comparison of magnetic resonance angiography and constructive interference in steady state-three-dimensional Fourier transformation magnetic resonance imaging in patients with hemifacial spasm

Although the decision to perform a microvascular decompression of the facial nerve is based on clinical history and assessment, preoperative imaging of the neurovascular relationships at the REZ is important to exclude a non-vascular cause or identify dolichoectatic vessels that might influence the surgical approach. We designed the current study to compare the specificity and sensitivity of gadolinium-enhanced 3D fast inflow with steady state precession (FISP) MRA with CISS. The imaging findings of 47 patients that had microvascular decompression for hemifacial spasm were retrospectively reviewed in a single blind fashion. The 47 non-symptomatic sides served as controls. Neurovascular contact could be seen in 13/47 (27.6%) in routine T2 axial scans, in 22/35 (62.8%) in high resolution T2W, in 18/34 (52.9%) in the case of MRA, and in all cases (13) when the CISS sequence was used. This study demonstrated 56.2% sensitivity and 50% specificity for MRA with gadolinium enhancement, whereas the CISS sequence can achieve a sensitivity of 100% in correctly demonstrating neurovascular compression in HFS. Overall accuracy of the two methods was 55.8 and 100% for MRA and CISS, respectively. The CISS sequence is superior in identifying neurovascular compression when compared with MRA. Preoperative knowledge of the compressing vessel has counselling implications and the higher risk of complications should be communicated to the patient. Due to cost and time implications we suggest that MR-CISS imaging replace the enhanced MRA sequence in the detailed preoperative MR assessment of hemifacial spasm.

Hemifacial Spasms and Involuntary Facial Movements. Role of Magnetic Resonance in the Diagnostic Work-up. A Case Report

Caution is required when dealing with patients presenting hemifacial spasm as the symptom is common to many disorders (tumours, herpes zoster, a frigore paralysis, neurovascular conflict…). Often no reasonable cause of the spasm is found, but treatment must be attempted because hemifacial spasm can be highly debilitating. We describe a case of hemifacial spasm, initially deemed idiopathic, in which MRI demonstrated neurovascular conflict as the cause. It is not always easy to find a clear MRI pattern, but if the scan identifies the tortuousness of the arteries in the vicinity of the VII nerve root exit, it is highly probable that this is the true cause of hemifacial spasm. Even when it is not possible to identify this pattern, neurovascular compression cannot be ruled out. The good results of microvascular decompression in patients without a typical MRI pattern suggest that MRI is specific, but not always sensitive. There is no consensus in the literature on the sensitivity of MRI in the detection of neurovascular compression and values vary widely. It is generally believed that experience and different performance of the MR systems strongly influence the diagnosis of neurovascular conflict.

Visualization of the intracisternal angioarchitecture at the posterior fossa by use of image fusion

OBJECTIVE

Magnetic resonance (MR) images most clearly visualize intracranial tissues but have some limitations in terms of detailed analysis of the intracisternal vasculature. To compensate for these shortcomings, an image fusion of three-dimensional digital subtraction angiography (DSA) and MR images, DSA-MR fusion, has been developed. The goal of this study was to evaluate the usefulness of DSA-MR fusion for the visualization of the intracisternal arteries and veins at the posterior fossa.

METHODS

Ten consecutive patients (five with neurovascular compression syndrome and five with brain tumors) underwent preoperative DSA-MR fusion. The DSA-MR fusion images were compared with intraoperative findings.

RESULTS

Image fusion was performed within 20 minutes, and the registration error was insignificant in all cases. Image fusion successfully visualized the clear three-dimensional relationships among the intracisternal arteries and veins, cranial nerves, brain tissues, and a lesion, and a specific vessel was easily identified. The findings of the DSA-MR fusion images were surgically confirmed in all patients.

CONCLUSION

Using this advanced image fusion technique coupled with its reasonable postprocessing time, neurosurgeons may more easily and precisely understand the surgical anatomy before surgery than analyzing three-dimensional DSA and MR images separately.

Imaging of the upper cranial nerves I, III–VIII, and the cavernous sinuses

This article discusses the upper cranial nerves (I, III-VIII) and their anatomy as it pertains to intra-axial nuclei and tracts, cisternal portions, and extracranial portions. In addition, the most common pathologic processes affecting the upper cranial nerves are discussed and illustrated. Because the evaluation of small structures requires imaging techniques that provide high resolution and contrast, MR imaging is the examination of choice. CT still plays a limited but important role in the evaluation of intraosseous portions of some cranial nerves.

Three-dimensional visualization of neurovascular relationships in the posterior fossa: technique and clinical application

Object. The goal of this study was to describe the authors' technique for three-dimensional (3D) visualization of neurovascular relationships in the posterior fossa at the surface of the brainstem. This technique is based on the processing of high-resolution magnetic resonance (MR) imaging data. The principles and technical details involved in the accurate simultaneous visualization of vessels and cranial nerves as tiny structures are presented using explicit and implicit segmentation as well as volume rendering.

Methods. In this approach 3D MR constructive interference in steady state imaging data served as the source for image processing, which was performed using the Linux-based software tools SegMed for segmentation and Qvis for volume rendering. A sequence of filtering operations (including noise reduction and closing) and other software tools such as volume growing are used for a semiautomatic coarse segmentation. The subsequent 3D visualization in which implicit segmentation is used for the differentiation of cranial nerves, vessels, and brainstem is achieved by allocating opacity and color values and adjusting the related transfer functions. This method was applied to the presurgical evaluation in a consecutive series of 55 patients with neurovascular compression syndromes and the results were correlated to surgical findings. The potential for its use, further developments, and remaining problems are discussed.

Conclusions. This method provides an excellent intraoperative real-time virtual view of difficult anatomical relationships.

Analysis and 3-dimensional visualization of neurovascular compression syndromes

RATIONALE AND OBJECTIVES

Neurovascular compression syndromes are currently examined with 2-dimensional representations of tomographic volumes. To overcome this drawback, coarse segmentation followed by direct volume rendering of magnetic resonance (MR) data is introduced supporting a detailed 3-dimensional analysis of the related structures.

MATERIALS AND METHODS

This approach is based on MR-CISS (constructive interference in steady state) volumes providing the required high resolution to achieve an improved spatial understanding. In relation to the size of the involved nerves and vessels, an explicit segmentation is extremely difficult. Therefore, a semi-automatic preprocessing sequence was developed consisting of noise reduction, morphologic filtering, and volume growing. To delineate the target structures within the segmented and labeled subvolumes, interactive direct volume rendering was applied that allows delineating the target structures in the area of the cerebrospinal fluid with implicit segmentation based on predefined transfer functions assigning opacity and color values to the intensity values of the image data. For a further improved analysis, registration of the MR-CISS volumes with MR angiography is recommended to support differentiating vessels and nerves on the one side and arteries and veins on the other.

RESULTS

The presented method was applied in a consecutive series of 47 cases of different neurovascular compression syndromes, supporting the presurgical analysis of the image data. Additionally, the results were compared with the operative findings.

CONCLUSION

Overall, this approach contributes significantly to an optimized 3-dimensional analysis and understanding of neurovascular compression syndromes. Based on the obtained results, it is of high value for the planning of surgery.

Imaging of the upper cranial nerves I, III-VIII, and the cavernous sinuses

This article discusses the upper cranial nerves (I, III-VIII) and their anatomy as it pertains to intra-axial nuclei and tracts, cisternal portions, and extracranial portions. In addition, the most common pathologic processes affecting the upper cranial nerves are discussed and illustrated. Because the evaluation of small structures requires imaging techniques that provide high resolution and contrast, MR imaging is the examination of choice. CT still plays a limited but important role in the evaluation of intraosseous portions of some cranial nerves.

Role of postoperative magnetic resonance imaging after microvascular decompression of the facial nerve for the treatment of hemifacial spasm

OBJECTIVE

This study was performed to investigate the role of postoperative three-dimensional short-range magnetic resonance angiography in the prediction of clinical outcomes after microvascular decompression (MVD) for the treatment of hemifacial spasm.

METHODS

We examined pre- and postoperative magnetic resonance imaging scans obtained between March 1999 and May 2000 for 122 patients with hemifacial spasm, to evaluate the degree of detachment of the vascular contact and changes in the positions of offending vessels. The degree of vascular decompression of the facial nerve root was classified into three groups, i.e., contact, partial decompression, or complete decompression. Contact was defined as unresolved compression, as indicated by postoperative three-dimensional short-range magnetic resonance angiography. Partial decompression was defined as incompletely resolved compression; vascular indentation of the facial nerve was improved, but contact with the facial nerve remained. Complete decompression was defined as completely resolved compression. These findings were compared with the surgical findings and clinical outcomes.

RESULTS

Of 122 patients with MVD, complete decompression of offending vessels at the root entry zone of the facial nerve was observed for 106 patients (86.9%), partial decompression was observed for 10 patients (8.2%), and contact with offending vessels was observed for 6 patients (4.9%) by using postoperative three-dimensional short-range magnetic resonance angiography. Our study demonstrated that the types of offending vessels affected neither the degree of decompression of the root entry zone of the facial nerve nor surgical outcomes (P > 0.05). Also, there was no significant relationship between the degree of decompression and improvement of symptoms (P > 0.05). Furthermore, there was no significant relationship between the degree of decompression and the timing of symptomatic improvement (P > 0.05).

CONCLUSION

Our data suggest that MVD of the facial nerve alone may not be sufficient to resolve symptoms for all patients with hemifacial spasm. Therefore, unknown factors in addition to vascular compression may cause symptoms in certain cases, and it may be necessary to remove those factors, simultaneously with MVD, to obtain symptom resolution.

Superior oblique myokymia: magnetic resonance imaging support for the neurovascular compression hypothesis

Superior oblique myokymia is a rare movement disorder thought to be caused by vascular compression of the trochlear nerve. Direct display of such neurovascular compression by magnetic resonance imaging has been lacking. The goal of this study was to assess the presence of neurovascular contacts in patients with superior oblique myokymia, using a specific magnetic resonance imaging protocol. A total of 6 patients suffering from right superior oblique myokymia underwent detailed neuro-ophthalmological examination, which showed tonic or phasic eye movement. All patients underwent magnetic resonance imaging, using a magnetic resonance imaging Fourier transform constructive interference in steady-state sequence in combination with magnetic resonance imaging time of flight magnetic resonance arteriography both before and after the administration of Gd-DTPA. With this protocol, the trochlear nerve could be visualized on 11 of 12 sides (92%). Arterial contact was detected at the root exit zone of the symptomatic right trochlear nerve in all 6 patients (100%). No arterial contact was identified at the root exit zone of the asymptomatic left trochlear nerve in any of the 5 left nerves visualized. In conclusion, superior oblique myokymia can result from neurovascular contact at the root exit zone of trochlear nerve, and therefore should be considered among the neurovascular compression syndromes.

Preoperative assessment of trigeminal neuralgia and hemifacial spasm using constructive interference in steady state-three-dimensional Fourier transformation magnetic resonance imaging

Results of microvascular decompression (MVD) for trigeminal neuralgia (TN) and hemifacial spasm (HFS) may be improved by accurate preoperative assessment of neurovascular relationships at the root entry/exit zone (REZ). Constructive interference in steady state (CISS)-three-dimensional Fourier transformation (3DFT) magnetic resonance (MR) imaging was evaluated for visualizing the neurovascular relationships at the REZ. Fourteen patients with TN and eight patients with HFS underwent MR imaging using CISS-3DFT and 3D fast inflow with steady-state precession (FISP) sequences. Axial images of the cerebellopontine angle (CPA) obtained by the two sequences were reviewed to assess the neurovascular relationships at the REZ of the trigeminal and facial nerves. Eleven patients subsequently underwent MVD. Preoperative MR imaging findings were related to surgical observations and results. CISS MR imaging provided excellent contrast between the cranial nerves, small vessels, and cerebrospinal fluid (CSF) in the CPA. CISS was significantly better than FISP for delineating anatomic detail in the CPA (trigeminal and facial nerves, petrosal vein) and abnormal neurovascular relationships responsible for TN and HFS (vascular contact and deformity at the REZ). Preoperative CISS MR imaging demonstrated precisely the neurovascular relationships at the REZ and identified the offending artery in all seven patients with TN undergoing MVD. CISS MR imaging has high resolution and excellent contrast between cranial nerves, small vessels, and CSF, so can precisely and accurately delineate normal and abnormal neurovascular relationships at the REZ in the CPA, and is a valuable preoperative examination for MVD.

Microanatomy of the cerebellopontine angle and internal auditory canal: study with new magnetic resonance imaging technique using three-dimensional fast spin echo

OBJECTIVE

We report a new magnetic resonance imaging technique that uses three-dimensional fast spin echo and the minimum intensity projection method. Using this technique, detailed images of the cerebellopontine angle (CPA) and internal auditory canal (IAC) were obtained in normal volunteers and in patients with acoustic neuromas or hemifacial spasm.

METHODS

Ten normal volunteers, 44 patients with acoustic neuromas, and 31 patients with hemifacial spasm were studied using the three-dimensional fast spin echo magnetic resonance imaging protocol. The CPA and IAC were scanned by using a 1-mm slice thickness in the axial and parasagittal planes.

RESULTS

Normal anatomy was as follows. 1) The vestibulocochlear nerve was ovoid near the brain stem and changed to a slightly crescentic configuration (C shape) as it traveled laterally. 2) Separation of the cochlear and vestibular nerves was observed near the central part of the IAC. 3) Discrimination between the superior and inferior vestibular nerves was also possible near the fundus of the IAC. 4) The facial nerve was easily identifiable as a discrete nerve at the anterior aspect of the vestibulocochlear nerve. 5) The meatal loop of the cerebellar artery was located medial to the porus in 44% of 95 CPAs and reached the porus or protruded into the porus in 56%. Acoustic neuromas were as follows. 1) In a patient with a very small intracanalicular tumor, the nerve on which the tumor was located could be identified. 2) In 22 of 44 acoustic neuromas, cerebrospinal fluid was present between the tumor and the fundus of the IAC. Hemifacial spasm was as follows. The relationship between the responsible artery and the facial nerve could be precisely observed.

CONCLUSION

The three-dimensional fast spin echo method offers ultrahigh-resolution images, which are extremely useful in understanding the surgical anatomy of the CPA and IAC.

[Familial hemifacial spasm: report of 2 cases]

The authors report the clinical and angiographical findings of two cases of familial hemifacial spasm. This is the fifth description in the literature and presents mother and daughter at the ages of 76 and 51 respectively, in whom the left side was affected. They underwent exams of angioresonance that showed dolichobasilar with left side origin in both patients. The exams also demonstrated postero-inferior cerebellar artery very developed and irregularities in the walls of the vertebral and basilar arteries suggestive of arteriosclerosis in the mother and slightly elongated intracranial vessels in the daughter. Literature review and etiology data of the hemifacial spasm are focused.

Pontine veins. MRI cross-sectional anatomy

The pons is covered by a rich venous network offering numerous vascular landmarks in MRI and during surgery. We present an original study of the veins as they appear on MR multiplanar scans after gadolinium IV injection. This prospective study is based on 40 consecutive patients with normal posterior fossa structures. One of the major venous collectors follows the pons: the superior petrosal v. was identified on MRI in 95% of our cases. Its hooklike extremity drains into the superior petrosal sinus. The inferior petrosal v. was never identifiable. The superficial pontine venous network are identified in 72.5% of cases in the axial plane and were organised in longitudinal and transverse collectors, whose MR aspects are presented here.

Vascular compressive abducens nerve palsy disclosed by magnetic resonance imaging

PURPOSE

To assess magnetic resonance imaging as a diagnostic tool of neurovascular compression in a patient with abducens nerve palsy.

METHODS

We performed magnetic resonance imaging of the brainstem of a 46-year-old patient with left abducens nerve palsy using spoiled gradient recalled acquisition in the steady state (SPGR), which allows high-resolution T1-weighted imaging and detection of the arteries across the plane of slices as a high-signal-intensity area.

RESULTS

Computed tomography of the brain was unremarkable except for leftward shifting of the basilar artery. As disclosed by magnetic resonance imaging with the SPGR, the right vertebral artery was shifted to the left and joined with the left vertebral artery, and the left abducens nerve was compressed by the vertebral artery. No other abnormal signals were seen in the brainstem.

CONCLUSIONS

These findings suggest that the abducens nerve palsy in this patient was caused by vascular compression at the root exit zone. Magnetic resonance imaging with the SPGR is useful for the diagnosis of vascular compressive neuropathy.

The veins of the medulla oblongata: MRI cross-sectional anatomy

Magnetic resonance imaging (MRI) has progressively become the major or even the only imaging procedure for displaying the vascular relationships of the brainstem in the context of infra-tentorial lesions. In order to assess the MR sectional anatomy of the bulbar vv. 40 normal patients were examined in the MR axial, frontal and sagittal planes after gadolinium i.v. injection. The bulbar venous networks were inconstantly visualised: anterior vv. (16%). posterior (3%), lateral (8%). The vein of the lateral recess of the fourth ventricle was constant in the three planes; the inferior petrosal sinus could be seen in 82% of cases. Their relation with the posterior fossa structures are emphasised and discussed.