Neurogenic hypertension. A new MRI protocol for the evaluation of neurovascular compression of the cranial nerves IX and X root-entry zone

Efficacy of microvascular decompression on the vascular compression type of neurogenic hypertension: A meta-analysis

OBJECTIVE

Neurogenic hypertension is a type of hypertension characterized by increased sympathetic activity. Vascular compression is one of the pathogenic mechanisms of neurogenic hypertension. The sample sizes of currently available studies on MVD in the treatment of hypertension are small, and the results are considerably different. Therefore, we conducted a meta-analysis of the previous literature to obtain the most realistic efficiency and analyzed the current situation of MVD as a treatment option of the vascular compression type of neurogenic hypertension.

METHOD

We systematically searched and identified relevant studies published before July 2019 from PubMed and Embase. Six studies involving 162 participants were included into our final analysis.

RESULT

The data showed that the effective rate of MVD was 70.1% (95% CI: 0.602-0.801). The most common offending vessel was PICA (29.9%), followed by VA/BA (23.9%) and VA/BA plus PICA (12.7%). Complications were mostly related to the VII, VIII, IX, and/or X cranial nerve dysfunction.

CONCLUSION

MVD as a treatment option of the vascular compression type of neurogenic hypertension is effective and safe. In spite of this conclusion, more prospective studies are needed to confirm it. On the other hand, a diagnostic method with higher sensitivity and specificity is necessary.

Primary hypertension and neurovascular compression: a meta-analysis of magnetic resonance imaging studies

Object

Several studies have suggested that neurovascular compression (NVC) of the brainstem might be a cause of hypertension. Because this compression syndrome might be demonstrated by MR imaging studies, several authors have tried to assess its prevalence in small series of patients with hypertension. This article presents a meta-analysis of these studies.

Methods

The studies reviewed by the authors were based on MR imaging and included the presence of left-sided NVC of the left rostral ventrolateral medulla oblongata (RVLM) and/or the cranial nerves IX and X root entry zone in patients with apparent primary hypertension compared with normotensive patients. Several studies also included patients with secondary hypertension as an additional control group, which is analyzed separately.

Results

Meta-analysis included data from 14 studies (597 patients with primary hypertension and 609 controls). The effect size was OR 2.68 (95% CI 1.51–4.75, p = 0.001) (random effect), which is consistent with the hypothesis that NVC of the left RVLM is more frequent in patients with apparent primary hypertension compared with normotensive individuals. Stratification for the study design revealed an effect size for prospective studies of OR 1.97 (95% CI 0.74–5.30, p = 0.178) and for retrospective studies of OR 3.36 (95% CI 1.66–6.79, p = 0.001).

Conclusions

This meta-analysis indicates a statistically significant effect size for left-sided NVC in apparent primary hypertension. However, this effect is absent if subanalysis is confined to prospective studies.

Cisternal segments of the glossopharyngeal, vagus, and accessory nerves: detailed magnetic resonance imaging-demonstrated anatomy and neurovascular relationships

OBJECT

The aim of this study was to determine whether high-resolution MR imaging is suitable for identifying and differentiating among the nerve root bundles of the glossopharyngeal (cranial nerve [CN] IX), vagus (CN X), and accessory nerves (CN XI) as well as any adjacent vessels.

METHODS

Twenty-five patients (50 sides) underwent MR imaging using the 3D constructive interference in steady-state (CISS) sequence, as well as noncontrast and contrast-enhanced 3D time-of-flight (TOF) MR angiography. Two individuals scored these studies by consensus to determine how well these sequences displayed the neurovascular contacts and nerve root bundles of CNs IX and X and the cranial and spinal roots of CN XI. Landmarks useful for identifying each lower CN were specifically sought.

RESULTS

The 3D CISS sequence successfully depicted CNs IX and X in 100% of the sides. Nerve root bundles of the cranial segment of CN XI were identified in 88% of the sides and those of the spinal segment of CN XI were noted in 93% of the sides. Landmarks useful in identifying the lower CNs included the vagal trigone, the choroid plexus of the lateral recess, the glossopharyngeal and vagal meatus, the inferior petrosal sinus, and the vertebral artery. The combined use of 3D CISS and 3D TOF sequences demonstrated neurovascular contacts at the nerve root entry or exit zones in 19% of all nerves visualized.

CONCLUSIONS

The combined use of 3D CISS MR imaging and 3D TOF MR angiography (with or without contrast) successfully displays the detailed anatomy of the lower CNs and adjacent structures in vivo. These imaging sequences have the potential to aid the preoperative diagnosis of and the presurgical planning for pathology in this anatomical area.

Glossopharyngeal neuralgia due to vascular compression by tortuous left posterior inferior cerebellar artery: a high strength (1.5 T) MRI study

Glossopharyngeal neuralgia is a rare condition with a frequency about 1% of that of trigeminal neuralgia. Vascular compression is a common and treatable cause of glossopharyngeal neuralgia. Microvascular decompression of the glossopharyngeal nerve is an effective treatment option for patients in whom the disease is caused by compression of the nerve by a blood vessel. Pre-operative detection of the pathology on imaging has become possible with high strength MRI imaging. We describe the case of a 54-year-old man with left glossopharyngeal neuralgia. Constructive interference in steady-state (CISS) and flow sensitive Gradient Echo MRI sequences clearly demonstrated the compression of the IX nerve by the left posterior inferior cerebellar artery (PICA). The patient was operated upon and a Teflon graft was put in between the nerve and the vessel. The intra-operative photographs and post-operative images are also presented here. After surgery, the patient improved symptomatically with no recurrence of the symptoms in the follow-up period of about eight months.

Compression of the Rostral Ventrolateral Medulla by a Vagal Schwannoma of the Cerebellomedullary Cistern Presenting with Refractory Neurogenic Hypertension: Case Report

OBJECTIVE:

The rostral ventrolateral medulla is thought to serve as a final common pathway for the integration of central cardiovascular information and to be important for the mediation of central pressor responses. An association between essential hypertension and neurovascular compression of the rostral ventrolateral medulla has been reported. This may be mediated by an increase in sympathetic tone.

CLINICAL PRESENTATION:

Schwannomas arising from the lower cranial nerves (Cranial Nerves IX-XI) are rare, constituting only 3% of all intracranial schwannomas unassociated with neurofibromatosis. The majority of these tumors present as jugular foramen lesions and, less commonly, they occur along the extracranial course of these nerves. An intracisternal location is extremely rare. Fewer than 15 cases of pathologically proven intracisternal vagal schwannomas in the absence of neurofibromatosis have been reported.

INTERVENTION:

We report a case of vagal schwannoma in the cerebellomedullary cistern causing distortion of the vagal root entry zone and presenting with refractory neurogenic hypertension. Total microsurgical excision of this tumor, arising from one of the rootlets of the vagus nerve, was achieved. Immediately postoperatively, blood pressure decreased markedly, and despite our effort to maintain the blood pressure with fluids, the patient developed a cerebral infarction in the watershed zone.

CONCLUSION:

We discuss the proposed mechanism of hypertension, and the perioperative management, stressing blood pressure control. A review of the literature regarding vagal schwannomas is also presented. To the best of our knowledge, this is the first case report of a cerebellomedullary cistern vagal schwannoma presenting with neurogenic hypertension.

Utility of magnetic resonance cisternography using three-dimensional fast asymmetric spin-echo sequences with multiplanar reconstruction: the evaluation of sites of neurovascular compression of the trigeminal nerve

OBJECTIVE

To evaluate the utility of magnetic resonance (MR) cisternography using 3-dimensional (3D) fast asymmetric spin-echo (FASE) sequences with multiplanar reconstruction (MPR) for detection of the sites of neurovascular compression (NVC) in patients with trigeminal neuralgia.

STUDY DESIGN

Both MR cisternography with 3D-FASE sequences and MR angiography (MRA) were performed on 150 patients with clinical signs and symptoms that suggested trigeminal neuralgia. Results from the original MR cisternography with 3D-FASE sequences, the original MRA, and 4 reformatted images were used for interpretation. Images with inversion between black and white were used from the MR cisternography with 3D-FASE sequences to evaluate NVC. A diagnosis of NVC was made from the presence of vascular contact with the trigeminal nerve at the root entry zone (REZ) and the nature of the involved vessels. For the patients with NVC detectable on 3D-FASE or MRA images, the relationship between the clinically manifested regions and the NVC sites was also evaluated.

RESULTS

Of the 150 patients evaluated, 89 were deemed to have NVC. Of these 89 patients, 3 underwent surgery that identified the artery that was involved with the trigeminal nerve. The correlation between the clinically manifested regions and the NVC sites was significantly detectable using both 3D-FASE images and MRA in 89 patients with detectable NVC. The correlation coefficient using 3D-FASE imaging was a little higher than that using MRA. Of the 61 patients deemed not to have NVC, 6 were found to have brain tumors that invaded the root entry zone of the trigeminal nerve. However, the remaining 55 patients had no identifiable cause for trigeminal neuralgia. NVC was found in the asymptomatic side in 27 (18%) of the 150 patients with trigeminal neuralgia using MR cisternography with 3D-FASE sequences.

CONCLUSIONS

The technique of MR cisternography using 3D-FASE sequences with MPR is more accurate and useful than MRA for detection of the site of NVC in patients with trigeminal neuralgia. Patients with trigeminal neuralgia should be further examined using MR imaging to rule out a brain tumor. Radiologists should understand that a few subjects with no symptoms could show NVC with MR cisternography.

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.

Long-lasting improvement of arterial hypertension after surgical treatment of a foramen magnum meningioma: case report

BACKGROUND

Neurogenic arterial hypertension has been proposed to be caused by neurovascular compression in many cases. However, there is little reference to tumors causing hypertension by local compression of the vagal nerve or the ventrolateral medulla oblongata. The following case illustrates the effects of surgery for a meningioma of the foramen magnum on arterial hypertension.

CASE DESCRIPTION

A 54-year-old woman suffered from arterial hypertension for at least 7 months, for which she required a combined medical treatment regime. She suffered for 6 months from dizziness and tinnitus, more in the left ear than in the right. Neurologic examination revealed a horizontal fixation nystagmus and a mild left-sided hearing loss. Magnetic resonance imaging and computed tomographic angiography showed a contrast-enhancing tumor on the left side of the foramen magnum compressing the medulla oblongata close to the vertebral artery and vascularized by branches of the left PICA. Complete surgical extirpation was performed using a medial craniocervical approach. The tinnitus and dizziness were gone and hearing improved. Postoperatively, the arterial hypertension showed a long-lasting improvement (observation period 8 months) with only minimal medical treatment.

CONCLUSION

Based on our case, we conclude that tumors in close proximity to the ventrolateral medulla oblongata may induce neurogenic hypertension, similar to neurovascular compression.

Neurovascular contact and blood pressure response in young, healthy, normotensive men

BACKGROUND

Neurovascular contact (NVC) of the left rostral ventrolateral medulla has been implicated in the pathogenesis of "essential" hypertension, and recent studies suggest that this anomaly may be genetically determined. We therefore assessed the prevalence of this vascular anomaly in young normotensive volunteers. We also studied blood pressure, heart rate reactivity, and changes in baroreflex sensitivity in response to mental and physical stress in a subset of subjects with positive and negative brainstem findings.

METHODS

Magnetic resonance imaging of the brainstem was performed in 113 young (aged 25 +/- 8 years), normotensive male volunteers. Baroreflex sensitivity was then assessed in 13 subjects with positive brainstem findings and 20 subjects with negative findings.

RESULTS

Left-sided NVC was found in 19 subjects. Blood pressure levels, heart rate, and baroreflex sensitivity were similar in all groups. However, modulation of baroreflex sensitivity was reduced under mental and physical stress in subjects with a positive finding for NVC. Subjects with a positive finding also had a significantly lower body mass index than those with a negative finding.

CONCLUSIONS

Left-sided NVC is present in approximately one-fifth of young normotensive men, and may modulate the baroreceptor reflex under stress in these individuals.

Advanced magnetic resonance imaging techniques for patients with hemifacial spasm

PURPOSE

To review the underlying causes, diagnostic issues, and treatment of hemifacial spasm, with emphasis on advanced MRI techniques.

METHODS

Brief technical note.

RESULTS

High-resolution T1- and T2-weighted spin-echo and/or gradient echo imaging of the posterior fossa should be performed with the use of intravenous gadolinium for maximum contrast between CSF, vessel, and nerve. Magnetic resonance angiography is often useful, and new state-of-the-art sequences provide more detail.

CONCLUSIONS

As MRI techniques improve, diagnosis and treatment of patients with hemifacial spasm will become easier. Ophthalmologists should be aware of these new magnetic resonance techniques.

Neurovascular Contact of Cranial Nerve IX and X Root-Entry Zone in Hypertensive Patients

-Neurovascular contact of the left rostral ventrolateral medulla has been implicated in the pathogenesis of "essential" hypertension, and recent intervention studies suggest that surgical decompression of the ventrolateral medulla lowers blood pressure in these patients. We assessed the prevalence of this vascular anomaly in patients with essential hypertension by using an advanced MRI technique. We performed MRI of the brain stem in 125 hypertensive patients and in 105 age-matched, sex-matched, and body mass index-matched normotensive control subjects. Imaging of the root-entry zone of cranial nerves IX and X was performed by combining a high-resolution 3D constructive interference in steady-state sequence with a flow-sensitive time-of-flight technique, and images were independently assessed by 4 readers using predefined criteria. Left-sided neurovascular contact was found in 23% of the hypertensive patients and in 16% of the normotensive individuals (P:=0.12). Blood pressure level, heart rate, and number of antihypertensive medications in treated hypertensive patients were similar among patients with positive, borderline, and negative brain stem findings. Our findings cast doubt on the importance of left-sided neurovascular contact as a frequent cause of essential hypertension or as a major factor determining the severity of hypertension in patients with this anomaly.