Figure 1
Coronal MR images
Vascular Loop Syndrome In A Case Presenting With Hemi Facial Spasm
SectionNeuroradiology
Case TypeClinical Cases
AuthorsRania Zeitoun, MD, FRCR
Connected authors
52 years, male
Clinical History
A male patient, 52 years old, suffering from left hemi facial spasm for more than 1 year.
Imaging Findings
Magnetic Resonance Imaging (MRI), Axial thin cuts at the posterior fossa (using 3D fast imaging employing steady-state acquisition (3D-FIESTA) sequence) revealed elongated ectatic left vertebral artery that is seen extending deep into the inferior part of the left cerebello pontine angle. The tortous left vertebral artery is seen impinging the facial nerve at its root exit zone. The left vertebral artery is ectatic, as apparent on coronal T2 images. Sagittal T2 images revealed associated partial agenesis of the corpus callosum. The posterior part of the body and the splenium are abscent while the rest of corpus callosum appears small sized.
Discussion
Background: Vascular loop syndromes describe neuro vascular compression disorders in which a vessel impinges one of the cranial nerves. The most commonly involved cranial nerves are the trigeminal (V) and facial (VII) nerves [1].
The facial nerve arises in the ponto medullary sulcus then passes, together with the vestibulo cochlear nerve, in the cerebello pontine angle (CPA) cistern directed toward the internal auditory canal. A vascular loop that contacts the facial nerve along its CPA course and especially while it arises from the ponto medullary sulcus where the vascular loop also compresses the brain stem at the root exit zone (RExZ), can result in neural irritation. The RExZ is considered a weak point, being the junction between central and peripheral myelination. At this point, demyelination is thought to be accelerated [2].
The involved offending vessels include: anterior inferior cerebellar artery (AICA), posterior inferior cerebellar artery (PICA) and ectatic vertebral artery [1-3].
Clinical perspective: Hemi-Facial spasm is characterized by abnormal paroxysms of tonic clonic contractions involving the peri orbital and peri oral muscles [2, 3].
Imaging perspective: Magnetic Resonance imaging (MRI) is the modality of choice in the work up of hemi facial spasm. It can reveal an aberrant course of a vascular structure and excludes other vascular and non vascular aetiologies [1, 2].
The posterior fossa is a crowded region with many small vital structures coursing the cisterns and canals; necessitating high resolution images. Axial thin posterior fossa cuts using 3D-FIESTA sequence offer high contrast heavy T2 images [2].
Images can identify the facial nerve at the CPA cistern and within the IAC. It can clearly show an aberrant vascular structure such as ectatic vertebral artery in the presented case. Alternatively it may reveal another vascular abnormality or non vascular CPA masses being the causative factor [1, 2].
Nevertheless, asymptomatic individuals may have imaging findings of a vessel offending or in contact with a nerve. Thus imaging findings alone do not constitute the diagnosis [3, 4].
Outcome: MRI revealing a vascular loop offending the facial nerve excludes other etiologies and directs the patient to micro vascular decompression as a surgical option [2].
Take home Message:
1) Optimized MRI is the diagnostic imaging modality in these cases.
2) Accurate clinical examination and clear notification of the presenting symptoms are essential to make the diagnosis.
3) High level of suspicion is required to prompt the search for an offending vessel on MRI in the appropriate clinical setting.
4) The imaging findings alone in absence of clinical symptoms do not make the diagnosis.
The facial nerve arises in the ponto medullary sulcus then passes, together with the vestibulo cochlear nerve, in the cerebello pontine angle (CPA) cistern directed toward the internal auditory canal. A vascular loop that contacts the facial nerve along its CPA course and especially while it arises from the ponto medullary sulcus where the vascular loop also compresses the brain stem at the root exit zone (RExZ), can result in neural irritation. The RExZ is considered a weak point, being the junction between central and peripheral myelination. At this point, demyelination is thought to be accelerated [2].
The involved offending vessels include: anterior inferior cerebellar artery (AICA), posterior inferior cerebellar artery (PICA) and ectatic vertebral artery [1-3].
Clinical perspective: Hemi-Facial spasm is characterized by abnormal paroxysms of tonic clonic contractions involving the peri orbital and peri oral muscles [2, 3].
Imaging perspective: Magnetic Resonance imaging (MRI) is the modality of choice in the work up of hemi facial spasm. It can reveal an aberrant course of a vascular structure and excludes other vascular and non vascular aetiologies [1, 2].
The posterior fossa is a crowded region with many small vital structures coursing the cisterns and canals; necessitating high resolution images. Axial thin posterior fossa cuts using 3D-FIESTA sequence offer high contrast heavy T2 images [2].
Images can identify the facial nerve at the CPA cistern and within the IAC. It can clearly show an aberrant vascular structure such as ectatic vertebral artery in the presented case. Alternatively it may reveal another vascular abnormality or non vascular CPA masses being the causative factor [1, 2].
Nevertheless, asymptomatic individuals may have imaging findings of a vessel offending or in contact with a nerve. Thus imaging findings alone do not constitute the diagnosis [3, 4].
Outcome: MRI revealing a vascular loop offending the facial nerve excludes other etiologies and directs the patient to micro vascular decompression as a surgical option [2].
Take home Message:
1) Optimized MRI is the diagnostic imaging modality in these cases.
2) Accurate clinical examination and clear notification of the presenting symptoms are essential to make the diagnosis.
3) High level of suspicion is required to prompt the search for an offending vessel on MRI in the appropriate clinical setting.
4) The imaging findings alone in absence of clinical symptoms do not make the diagnosis.
Differential Diagnosis List
Vascular Loop Syndrome
Vascular aneurysm
AVM
CPA masses: shwannoma
Final Diagnosis
Vascular Loop Syndrome
References
[1] Harnsberger H.R.,Wiggins R.H.,Hudgins P.A. et al (2004) VASCULAR LOOP COMPRESSION, CPA-lAC. Dagnostic Imaging Series: Head And Neck Chapter 1-1, pages: 46 and 47
[2] Elaini S., Magnan J., Deveze A. and Girard N. (2013) Magnetic resonance imaging criteria in vascular compression syndrome. The Egyptian Journal of Otolaryngology 29:10–15
[3] Suthipongchai S, Chawalparit O, Churojana A, Poungvarin N. (2004) Vascular loop compressing facial nerve in hemifacial spasm: demonstrated by 3D-phase contrast magnetic resonance angiography in 101 patients. J Med Assoc Thai 87(3):219-24 (PMID: 15117036)
[4] Tan E-K and Chan LL (2004) Clinico-radiologic correlation in unilateral and bilateral hemifacial spasm. J Neurol Sci 222(1–2):59–64 (PMID: 15240197)
Case information
| URL: | https://www.eurorad.org/case/13038 |
| DOI: | 10.1594/EURORAD/CASE.13038 |
| ISSN: | 1563-4086 |
License
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Figure 2
Sagittal T2 images
Associated partial agenesis of the corpus callosum
Sagittal T2 images
Associated partial agenesis of the corpus callosum
Zeitoun R., MD,FRCR
Zeitoun R., MD,FRCR
