A case-controlled MRI/MRA study of neurovascular contact in hemifacial spasm

Bridge-layered decompression technique for vertebral artery-involved hemifacial spasm: technical note

BACKGROUND

Hemifacial spasm (HFS) is most effectively treated with microvascular decompression (MVD). However, there are certain challenges in performing MVD for HFS when the vertebral artery (VA) is involved in compressing the facial nerve (VA-involved). This study aimed to introduce a "bridge-layered" decompression technique for treating patients with VA-involved HFS and to evaluate its efficacy and safety to treat patients with HFS.

METHODS

A single-center retrospective analysis was conducted on the clinical data of 62 patients with VA-involved HFS. The tortuous trunk of VA was lifted by a multi-point "bridge" decompression technique to avoid excessive traction of the cerebellum and reduce the risk of damage to the facial-acoustic nerve complex. To fully decompress all the responsible vessels, the branch vessels of VA were then isolated using the "layered" decompression technique.

RESULTS

Among the 62 patients, 59 patients were cured immediately after the surgery, two patients were delayed cured after two months, and one had occasional facial muscle twitching after the surgery. Patients were followed up for an average of 19.5 months. The long-term follow-up results showed that all patients had no recurrence of HFS during the follow-up period, and no patients developed hearing loss, facial paralysis, or other permanent neurological damage complications. Only two patients developed tinnitus after the surgery.

CONCLUSION

The "bridge-layered" decompression technique could effectively treat VA-involved HFS with satisfactory safety and a low risk of hearing loss. The technique could be used as a reference for decompression surgery for VA-involved HFS.

How to face the hemifacial spasm: challenges and misconceptions

Hemifacial spasm (HFS) is characterised by intermittent, brief or sustained, repetitive contractions of the muscles innervated by one facial nerve. It is one of the most frequent movement disorders affecting the face. However common and allegedly straightforward to diagnose, it might reveal as a challenge for clinicians in various situations. Indeed, it often needs prior exclusion of many other movement disorders affecting the face, with frequent phenomenological overlaps with blepharospasm, post-facial palsy, facial motor tics, etc. The clinical diagnosis shall be supported by modern brain imaging techniques, and sometimes electromyography, as some particular aetiologies may require specific treatment. Primary forms are associated with vascular compression of the ipsilateral seventh cranial nerve, whereas secondary forms can be caused by any injury occurring on the facial nerve course. This article proposes a global and organised approach to the diagnosis, and the ensuing therapeutic options, as many practitioners still use some inefficient medications when they encounter a case of facial spasm.

Hemifacial spasm through the last three decades: From etiology to efficacy and safety of long-term botulinum toxin treatment

BACKGROUND

Hemifacial spasm (HFS) is an uncommon movement disorder characterized by involuntary contractions of muscles innervated by the facial nerve. The aim of this study is to analyze the etiology of HFS as well as the efficacy and safety of long-term botulinum toxin type A (BTX-A) treatment.

METHODS

Retrospective study including 125 patients with HFS treated with BTX-A from 1993 to 2019. Demographic and etiological variables as well as doses, number of sessions of BTX-A, infiltrated muscles, therapeutic response according to Patient Global Impression of Change Scale (PGIC-S), side effects and adjuvant treatments were analyzed. In addition, these variables were compared according to the etiology (idiopathic versus secondary).

RESULTS

92 patients (73.6%) were women and the mean age at diagnosis was 58.63 years (SD 15.4). The etiology was idiopathic in 79 patients (63.2%), 17.6% were secondary to Bell's palsy, 14.4% to vascular compression and 2.4% to tumors. A higher total dose per session was observed in the secondary group. PGIC-S showed a good response in 96% of cases. 16 patients (12.8%) required pharmacological concomitant treatment. 59 patients (47.2%) developed side effects. Transient eyelid ptosis and facial weakness were the most common.

CONCLUSIONS

The structural origin of a significant number of cases of HFS makes essential to complete an etiological diagnosis in all patients. In addition, the existence of a secondary cause could be associated with greater doses of BTX-A to achieve a good response. Regardless the etiology, long-term treatment with BTX-A in HFS is safe and effective.

Prevalence and Associated Factors of Neurovascular Contact in Patients With Hemifacial Spasm

PURPOSE

This study aimed to observe the prevalence and associated factors of neurovascular contact hemifacial spasm (HFS).

DESIGN

This was a cross-sectional analytical study.

METHODS

Medical records of patients with HFS in a neuro-ophthalmology clinic in Thailand between June 2008 and June 2012 were reviewed. A positive magnetic resonance imaging finding was defined as an adjacent variant vessel that directly compressed or placed pressure on the affected facial nerve. Prevalence and associated factors were analyzed.

RESULTS

A total of 60 participants were enrolled, composed of 12 male patients and 48 female patients with a median age of 54 years [interquartile range (IQR), 44.0-64.75] and a disease duration ranging from 4 months to 16 years (median, 2 years; IQR, 1.0-6.0). The prevalence of neurovascular contact HFS was 41.7%. Neurovascular contact HFS was more prevalent among women, with an overall ratio of 3.33. In age group analysis, the prevalence was higher among older patients. In univariate analysis, right-sided symptoms and diabetes mellitus were statistically significant in their association with neurovascular contact HFS (P = 0.040 and P = 0.029, respectively). Right-sided symptoms were significant in a multiple logistic regression analysis (P = 0.038), with an odds ratio of 3.30 [95% confidence interval (CI), 1.07-10.15]. Diabetes mellitus was not statistically significant (P = 0.051), with an odds ratio of 9.99 (95% CI 0.99-96.34).

CONCLUSIONS

The prevalence of neurovascular contact in patients with HFS was 41.7%. Right-sided symptoms were significantly associated with this condition.

Misdiagnosis of hemifacial spasm is a frequent event in the primary care setting

Primary hemifacial spasm (HFS) is characterized by irregular and involuntary contraction of the muscles innervated by the ipsilateral facial nerve. Treatment controls symptoms and improves quality of life (QoL). Objective : Evaluate the initial diagnosis and treatment of HFS prior to referral to a tertiary center. Method : We interviewed through a standard questionnaire 66 patients currently followed in our center. Results : Mean age: 64.19±11.6 years, mean age of symptoms onset: 51.9±12.5 years, male/female ratio of 1:3. None of the patients had a correct diagnosis in their primary care evaluation. Medication was prescribed to 56.8%. Mean time from symptom onset to botulinum toxin treatment: 4.34 ±7.1 years, with a 95% satisfaction. Thirty percent presented social embarrassment due to HFS. Conclusion : Despite its relatively straightforward diagnosis, all patients had an incorrect diagnosis and treatment on their first evaluation. HFS brings social impairment and the delay in adequate treatment negatively impacts QoL.

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.

The many faces of hemifacial spasm: differential diagnosis of unilateral facial spasms

Hemifacial spasm is defined as unilateral, involuntary, irregular clonic or tonic movement of muscles innervated by the seventh cranial nerve. Most frequently attributed to vascular loop compression at the root exit zone of the facial nerve, there are many other etiologies of unilateral facial movements that must be considered in the differential diagnosis of hemifacial spasm. The primary purpose of this review is to draw attention to the marked heterogeneity of unilateral facial spasms and to focus on clinical characteristics of mimickers of hemifacial spasm and on atypical presentations of nonvascular cases. In addition to a comprehensive review of the literature on hemifacial spasm, medical records and videos of consecutive patients referred to the Movement Disorders Clinic at Baylor College of Medicine for hemifacial spasm between 2000 and 2010 were reviewed, and videos of illustrative cases were edited. Among 215 patients referred for evaluation of hemifacial spasm, 133 (62%) were classified as primary or idiopathic hemifacial spasm (presumably caused by vascular compression of the ipsilateral facial nerve), and 4 (2%) had hereditary hemifacial spasm. Secondary causes were found in 40 patients (19%) and included Bell's palsy (n=23, 11%), facial nerve injury (n=13, 6%), demyelination (n=2), and brain vascular insults (n=2). There were an additional 38 patients (18%) with hemifacial spasm mimickers classified as psychogenic, tics, dystonia, myoclonus, and hemimasticatory spasm. We concluded that although most cases of hemifacial spasm are idiopathic and probably caused by vascular compression of the facial nerve, other etiologies should be considered in the differential diagnosis, particularly if there are atypical features.

Hemifacial spasm as a feature of Chiari malformation: case report

BACKGROUND AND IMPORTANCE

Hemifacial spasm has rarely been described as one of the presenting features of Chiari I malformation. We present a case in which we found an association between the two in the absence of a basilar impression.

CLINICAL PRESENTATION

A case of a 39-year-old man who presented with a disabling hemifacial spasm and was found to have Chiari I malformation as the possible cause is described. A foramen magnum decompression successfully relieved the hemifacial spasm. The patient remains symptom free at 20 months after the operation.

CONCLUSION

Neurosurgeons may want to consider foramen magnum decompression as first-line surgical treatment for hemifacial spasm when it coexists with Chiari I malformation. Chiari I malformation should be considered one of the rare causes of hemifacial spasm.

Taste sense in patients with hemifacial spasm

In the cerebellopontine angle cistern, the nervus intermedius (NI) runs close to the motor division of the facial nerve (FN). A vascular loop compressing the FN in patients with hemifacial spasm (HFS) can thus also affect the NI. However, to our knowledge, taste has not been investigated in patients with HFS. In this pilot study, we assessed the sense of taste quantitatively in 10 female patients with HFS using filter paper strips impregnated with four taste qualities (sweet, sour, salty, and bitter) at four concentrations. The taste score did not differ between the ipsilateral and contralateral sides. The taste score for salty on the ipsilateral side increased with disease duration. Our findings suggest that a vascular loop compressing the FN does not affect the function of the NI. Further studies with greater numbers of patients are needed to confirm our results.

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.

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.

Differences in improvement between patients with idiopathic versus neurovascular hemifacial spasm after botulinum toxin treatment

This study was performed to investigate the differences in response to botulinum toxin treatment between patients with idiopathic versus neurovascular hemifacial spasm. A total of 69 patients with hemifacial spasm were investigated prospectively with cranial magnetic resonance imaging and magnetic resonance angiography. Neurovascular contact was found in 23 patients. All patients were assessed with a severity scale and a disease awareness scale. After treatment, the patients with idiopathic hemifacial spasm improved significantly in terms of both severity and awareness scores, but the patients with neurovascular hemifacial spasm improved only in the awareness scores. In conclusion, patients with idiopathic hemifacial spasm experienced a greater improvement after treatment with botulinum toxin than did patients with neurovascular hemifacial spasm.

Clinical assessment of patients with primary and postparalytic hemifacial spasm: a retrospective study

OBJECTIVE: To compared the clinical features of 373 patients with primary and postparalytic hemifacial spasm (HFS). METHOD: Data analyzed were gender, ethnicity, age at symptom onset, disease duration, affected side, distribution of facial spasm at onset, hypertension, family history of HFS, previous history of facial palsy and latency between facial palsy and HFS. RESULTS:The prevalence of patients with Asian origin was similar in both groups such as female/male ratio, mean age at symptom onset, disease duration, affected side and distribution at onset of facial twitching. The upper left side of the face was the main affected region at onset. Almost 40% of the patients in both groups had hypertension. A prevalence of vascular abnormalities on the posterior fossa was seen in 7% and 12.5% of both groups. CONCLUSION: The clinical profile and radiological findings of patients with primary and postparalytic HFS are similar. The association of hypertension with vascular abnormalities and HFS was not frequent.

Microvascular decompression as a treatment for cranial nerve hyperactive dysfunction--a critical view

Neurovascular compression has been postulated as a probable mechanism for a large number of cranial nerve syndromes, with trigeminal neuralgia (TGN) as the prime example. Microvascular decompression (MVD) is often cited as the procedure of choice for treatment of medically refractory TGN. Arguments against these assumptions are: MRA studies indicate that vascular contact with the trigeminal nerve is present in most healthy individuals. Treatment results of MVD in multiple sclerosis patients with TGN are almost as good (at least in the short term) as in idiopathic cases. MVD is reported to provide pain relief even in TGN patients without visible neurovascular contact . In other syndromes of cranial nerve'hyperactive dysfunction'--vertigo, tinnitus and neurogenic hypertension--the documentation is even weaker.

Arterial Hypertension in Patients with Left Primary Hemifacial Spasm Is Associated with Neurovascular Compression of the Left Rostral Ventrolateral Medulla

The aim of the study was to clarify the relationship between neurovascular compression of the rostral ventrolateral medulla and arterial hypertension in patients with primary hemifacial spasm. We enrolled 82 patients with primary hemifacial spasm and 82 age- and sex-matched magnetic resonance imaging (MRI) controls of the posterior cranial fossa. Neurovascular compression of the rostral ventrolateral medulla was assessed by MRI, and its association with arterial hypertension was investigated. No significant differences were found in prevalence of arterial hypertension between patients with primary hemifacial spasm and control subjects (39.0 vs. 29.3%, p=0.19). Thirty-two percent of the patients with left primary hemifacial spasm (n=44) and 47% of the patients with right primary hemifacial spasm (n=38) were hypertensive. Neurovascular compression of the left rostral ventrolateral medulla was observed in 86% of those with left (ipsilateral) primary hemifacial spasm with arterial hypertension (n=14) and 33% of those with left (ipsilateral) primary hemifacial spasm without (n=30). The association between neurovascular compression of the left rostral ventrolateral medulla and arterial hypertension was significant in patients with left (ipsilateral) primary hemifacial spasm (p=0.0012), but not in patients with right (contralateral) primary hemifacial spasm (p=0.18). Neurovascular compression of the left rostral ventrolateral medulla was more frequently observed in hypertensive patients with left primary hemifacial spasm, and neurovascular compression of the left rostral ventrolateral medulla correlated with arterial hypertension in these patients. These results are of potential clinical importance for the treatment of primary hemifacial spasm with arterial hypertension.

Post-traumatic hemifacial spasm

We report an early-onset post-traumatic hemifacial spasm and discuss possible aetiology. A 20-year-old man was admitted to our hospital for observation because of an injury to the right frontotemporal region, resulting in drowsiness. On the second day in hospital, he developed peripheral paresis of the facial nerve on the right, followed by hemifacial spasm on the same side. He improved after corticosteroid treatment, and was discharged one week later almost completely recovered. The neuroradiology and clinical response suggest that the patient's hemifacial spasm was due to hyperexcitability of the facial nerve nucleus induced by a haematoma in the lower central pons.

Young onset hemifacial spasm

INTRODUCTION

Hemifacial spasm (HFS) frequently affects middle aged individuals and the clinical features and etiology have been well reported. However, there is limited data on the exact pathogenesis in young-onset HFS. If age is a major determinant of the etiology or influences the presentation of HFS, there may be clinical differences between the young and elderly HFS patients.

OBJECTIVES

We determined the prevalence, clinical and imaging features of young-onset HFS (age of onset<or=30 years) in a tertiary referral center. These data were compared with old onset (age of onset>or=65 years) HFS patients.

METHODS

We examined consecutive patients clinically diagnosed with HFS in a tertiary referral center. The clinical (demographics, clinical presentation, severity of HFS, associated medical conditions and other variables) and imaging findings of young onset patients and old onset patients were tabulated and compared.

RESULTS

Amongst 230 consecutive HFS patients, 15 (6.5%) were young-onset HFS and 50 (21.7%) were old-onset HFS. In the young-onset HFS, the mean age of onset of symptoms was 26.5+/-6.5 (6-30) years, with 80% women and 75.0% of young onset HFS having neurovascular compression (NVC) of the root exit zone (REZ) of the facial nerve on the ipsilateral side; 86.7% had initial onset of twitching in the upper eyelids that later progressed to the lower facial muscles. While the prevalence of hypertension, diabetes mellitus and other associated vascular disorders in late onset HFS was higher than in young onset groups, the clinical features and frequency of NVC of the facial REZ between the two groups were similar.

CONCLUSIONS

We demonstrated a 6.5% frequency of young-onset HFS in our cohort of HFS and their clinical presentation was similar to the old onset patients. Genetic, anatomic or other unidentified factors may contribute to NVC in young-onset HFS.

Case–control study of anxiety symptoms in hemifacial spasm

In a case-control study, we evaluated symptoms in nine different psychological domains in hemifacial spasm (HFS; using the Symptom Checklist-90R [SCL-90R]) and found the anxiety score to be significantly greater in HFS compared to healthy controls in both the univariate (P = 0.004) and multivariate analysis (adjusted for sex, age, marital status, and educational level; P = 0.002). Similar findings were obtained when comparison was made with an independent group of outpatient controls. Compared to outpatient controls, the HFS patients had a higher mean Hamilton Anxiety Rating Score (HAM-A; 10.0 +/- 8.0 [range, 0 to 28] vs. 5.0 +/- 5.0 [range, 0 to 25]; P = 0.004), and 19.5% had HAM-A score of 18 or above compared to 3.8% in controls (P = 0.02). Among the HFS patients, the mean anxiety score in SCL-90R was significantly higher in those defined with mild to severe anxiety under HAM-A compared to those without anxiety (74.0 +/- 6.0 vs. 48.0 +/- 13.0) (P < 0.0005). There was good correlation of the anxiety score with the HAM-A in HFS patients (r = 0.915; P < 0.0001). HFS patients with anxiety reported significant improvement of their symptoms (mean HAM-A score 19.0 +/- 5.0 vs. 11.0 +/- 6.0; P = 0.001) following appropriate management. As stress and anxiety can aggravate HFS, diagnosis and early management of anxiety symptoms can improve quality of life in these patients.

Childhood-onset hemifacial spasm: successful treatment with botulinum toxin

Hemifacial spasm is a disorder characterized by involuntary contractions of muscles innervated by the ipsilateral facial nerve. The majority of cases are of adult-onset. However, a few cases have been described in children. Detectable causes of pediatric hemifacial spasm include facial nerve compression by vasculature and brainstem masses. In the treatment of hemifacial spasm, surgical decompression of the facial nerve has been used with good results in both adults and children. However, surgical procedures have serious risks and should be used only in selected cases. Although injections of botulinum toxin type A have been successfully used in adult hemifacial spasm patients, to our knowledge there is no report of use of this indication in children. This report presents the first case of a pediatric patient with childhood-onset hemifacial spasm successfully treated with periorbital botulinum toxin injections. The literature on the subject is also reviewed.

Behind the facial twitch: depressive symptoms in hemifacial spasm

BACKGROUND

Depression impairs psychosocial and occupational functioning and contributes to significant morbidity and mortality. Hemifacial spasm (HFS) causes social embarrassment and visual and verbal disability.

OBJECTIVE

We examined; (1) the prevalence and predictive factors of depressive symptoms (Becks Depression Inventory (BDI) and clinical assessment) in HFS and (2) the sensitivity and specificity of BDI as a screening and diagnostic tool in HFS.

METHODS

A large cohort of HFS patients in a movement disorders clinic was clinically evaluated and the BDI self-administered by patients. Univariate analysis and multivariate logistic regression were undertaken to investigate the effect of age, gender, body-mass index, duration and severity of HFS on the outcome of BDI score. ROC (receiver operating characteristics) analysis was utilized to evaluate the sensitivity and specificity and discriminative property of the scale.

RESULTS

There were 90 HFS patients with a mean age of 54.4+11.1 (35-79) years, comprising of 58.9% women and with a mean severity HFS score of 2.9+0.8 (range 1-4). The mean BDI score was higher in depressed HFS than in non-depressed HFS (19.7+6.7 vs 4.2+4.9, p<0.0001). Female gender and a younger age were risk factors (p=0.07). In the multivariate analysis, the severity of HFS was an independent predictor of BDI scores (p<0.0001). The AUC was 97.1% suggesting excellent discriminative property of BDI. For cut-off score of 12/13, the sensitivity was 93.3%, specificity 94.7%, Positive Predictive Value 77.8% and Negative Predictive Value 98.6%.

CONCLUSIONS

The prevalence of depressive disorder in HFS was 16.7%, with younger women at greater risk. The severity of HFS was positively correlated with the severity of depressive symptoms. The BDI can be a complimentary screening and/or diagnostic instrument for depressive disorder in HFS. Early diagnosis of at-risk patients will prevent unnecessary morbidity and mortality.

Clinico-radiologic correlation in unilateral and bilateral hemifacial spasm

INTRODUCTION

Bilateral hemifacial spasm (HFS) is rare. Clinico-radiologic correlates utilizing advanced imaging techniques have not been systematically examined in bilateral HFS. The prevalence of bilateral HFS in an Asian population has not been clarified.

OBJECTIVES

We examined the prevalence and clinico-radiologic correlates of bilateral HFS in a clinic-based cohort and compared the clinical characteristics of unilateral HFS patients with and without contralateral neurovascular contact (NVC) in HFS.

METHODS

Patients clinically diagnosed with HFS were examined for bilateral symptoms. Imaging analysis involved the utilization of reformatted, multi-planar three-dimensional time-of-flight magnetic resonance angiography (3D-TOF MRA), and constructive interference at steady state (CISS-MR) sequences. The clinical and imaging data was compared between HFS with and without NVC.

RESULTS

Amongst 162 consecutive HFS patients, 2 (1.6%) had bilateral symptoms. Both patients had unilateral onset followed by bilateral and asynchronous facial contractions. The contralateral side of the face began to twitch at a mean of 1.5 years later. MRI/A revealed significant NVC of the root exit zone (REZ) of the facial nerve on the ipsilateral side with mild NVC contralaterally. The degree of NVC correlated with the clinical severity of the patients' symptoms. MRI/A analysis of 40 HFS patients with unilateral symptoms demonstrated NVC on the contralateral side in six patients (15%). The mean age and duration of symptoms were not different between HFS patients with and without contralateral NVC.

CONCLUSIONS

We demonstrated clinico-radiologic correlation between the clinical severity and the degree of NVC at the REZ of the facial nerve in bilateral HFS. Amongst unilateral HFS, there was no significant difference clinically between those with and without contralateral NVC. The low 1.6% prevalence of bilateral HFS in our Asian cohort was compatible with the rare prevalence in other ethnic populations.

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.

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.