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Neurology India, Vol. 58, No. 1, January-February, 2010, pp. 163-165 Neuroimage Simultaneous involvement of fifth and seventh nerves by vertebrobasilar dolichoectasia presenting as painful tic convulsif - Demonstrated by MR imaging Pallavi Aga, Umesh Parashari, Anit Parihar, Rajesh Yadav, Ragini Singh, Neera Kohli Department of Radiodiagnosis, C.S.M.M.U. (KGMU), Lucknow, UP, India Correspondence Address: Dr. Pallavi Aga, Type 4/87 SGPGI campus, Raebareli Road, Lucknow, U.P - 226 014, India, agapallavi@yahoo.co.in Date of Acceptance: 02-Nov-2009
Code Number: ni10048 DOI: 10.4103/0028-3886.60394 Painful tic convulsif (PTC) a rare entity, characterized by the coexistence of trigeminal neuralgia with hemifacial spasm was first described in 1920 by Cushing. [1] Since then only a few cases have been reported. Vascular compression by superior cerebellar artery (SCA) and vertebral artery or its branches is the commonest cause. [2] Simultaneous compression of both the nerves caused by dolichoectatic vertebrobasilar artery is uncommon and could easily be missed preoperatively. However, pre-operative diagnosis can be done by an appropriate magnetic resonance imaging (MRI) sequences. [3],[4] We describe a patient with PTC in whom compression of both trigeminal and facial nerves by vertebrobasilar dolichoectasia (VBD) has been demonstrated by MRI and magnetic resonance angiography (MRA). A 70-year-old hypertensive male was referred for MRI with two month history of left side trigeminal neuralgia and hemifacial spasm. MRI showed an ectatic vascular structure coursing anterolateral to the pons on the left side compressing and deforming the pons. [Figure - 1] and MRA showed an elongated and dilated right vertebral artery causing compression over the anterolateral pons and coursing to the left of midline to join the left ectatic vertebral artery. The elongated basilar artery, laying lateral to the plane of the clivus showed a high bifurcation; just above the plane of the suprasellar cistern. The diameter of the ectatic vertebral arteries was 6 mm and the basilar artery being 7 mm. [Figure - 2]. To better delineate the vascular structure, a unique sequence of 3D fast spoiled gradient recalled acquisition in the steady state (FSPGR) images, after administration of IV gadolinium, were obtained for mutiplanar reconstruction. The data acquired by 3D SPGR was reconstructed as 0.5 mm axial and coronal 3D reformations by the multi planar reformation (MPR) method at the MR workstation. The resulting images depicted the trigeminal nerve stretched, compressed and elongated at the root entry zone by the dolichoectatic left vertebral artery, however, no compression was noted in the cisternal course. Additional compression, stretching and deviation of the exit zone of left facial nerve by the same ectatic vertebral artery were also seen. [Figure - 3]a and b, [Figure - 4]. The pontine deformity was also better delineated in this sequence [Figure - 5].The complete MR imaging with the above mentioned sequences helped in clinching the diagnosis of VBD being the cause of trigeminal as well as facial nerve compression. The trigeminal nerve arises from a motor nucleus and three sensory nuclei and exits from the anterolateral aspect of the pons as a large sensory and a smaller motor root and then traverses through the pre-pontine cistern . [5] The facial nerve has its nuclei in the pons and the nerve fibers exit the brain at the inferior border of the pons. The root entry or exit zone is the point of change from central to peripheral myelin, varying between 10- 15 mm of length and is the most predisposed segment for vascular compression. [5] Increase in length and diameter of the intracranial arteries termed as dolichoectasia is the most common cause of vascular compression. Vertebrobasilar system is considered elongated if the basilar artery lies lateral to the margin of the clivus or dorsum sellae or if it bifurcates above the plane of the suprasellar cistern. Ectasia is considered to be present if the basilar artery has a diameter greater than 4-5 mm. [6] Patients with VBD manifestations are often hypertensive, older in age, and male with predominantly left-sided involvement. The postulated pathogenesis is severe atherosclerotic changes associated with hypertension. [7] However, sometimes VBD could also manifest at a younger age due to a congenital vascular anomaly. [8] Demonstration of simultaneous compression of both trigeminal and facial nerves utilizing various MR sequences like spoiled gradient recalled acquisition in the steady state (SPGR) sequences, fast imaging in steady precession (FISP) or constructive imaging in steady state (CISS) sequences together with MR angiography and 3-D imaging reconstructions from the data of SPGR MR imaging has been described. [9],[10],[11] In our patient, routine T1, T2, FLAIR and DWI sequences depicted an ectatic vessel to be the cause of the compression of brain stem and the nerves. MR imaging using post gadolinium SPGR sequences exquisitely demonstrated that the left trigeminal nerve was compressed, stretched and elongated due to ectatic left vertebral artery at the root entry zone, however the cisternal course appeared normal. The facial nerve was also stretched and compressed at the root entry zone by the ipsilateral ectatic vertebral artery. Probably this is the first pre-operative MRI demonstration of simultaneous seventh and fifth nerve compression by the same dolichoectatic vertebral artery. References
Copyright 2010 - Neurology India The following images related to this document are available:Photo images[ni10048f1.jpg] [ni10048f5.jpg] [ni10048f2.jpg] [ni10048f4.jpg] [ni10048f3.jpg] |
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