Clinical diagnosis
Case 176
【Progress】
He was recommended to receive brain surgery to isolate trigeminal nerve from superior cerebellar branch artery. But he refused the offer and he is now under watchful observation.
【Discussion】
Cranial nerves belong to peripheral nerve system. Peripheral nerve system and central nerve system are both covered with a myelin sheath which protect axon as well as facilitate electric signals. Peripheral myelin sheath composes of Schwann cells while central myelin sheath composes of oligodendrocytes (1, 2). There is a transition site between central nerve system and peripheral nerve system. The transition site is believed to be vulnerable to mechanical irritation by artery elongation and pulsation (1-4). The term of nerve vascular compression syndrome is used for symptoms caused by compression of vessels to the transition site.
It is imperative for imaging radiologists to be familiar with neurovascular compression syndrome. Especially, the relation of symptoms with the damaged nerve is critical to explore the damaged nerve. As neurovascular compression syndrome, there are several nerves involved: oculomotor nerve (III), trigeminal nerve (V), facial nerve (VII), vestibular nerve (VIII), glossopharyngeal nerve (IX), accessory nerve (XI) and medullary oblongata itself (3-5).
Oculomotor nerve and medullary oblongata are compressed by pivotal brain artery itself, while other brain nerves are compressed by brain branch artery. Oculomotor nerve paralysis is arisen by aneurysm compression at the bifurcation between internal carotid artery and posterior cerebral artery or at the bifurcation between basilar artery and superior cerebellar artery (4, 6). It causes sagging eyelids, ocular motility disorder and anisocoria. Medulla oblongata is compressed by elongation of vertebral artery (4). It causes contralateral discomfort feeling and /or muscle weakness.
The transitional sites of brain nerves exist within 5 mm from brainstem except vestibular cochlear nerve whose transitional site is approximately 10 mm (4, 5). The involved arteries are branches of superior cerebellar artery for trigeminal neuralgia (V), anterior inferior cerebellar branch artery (AICA) for compression to facial nerve (VII) or vestibular cochlear nerve (VIII) and posterior inferior cerebellar branch artery (PICA) for compression to [facial nerve (VII) or vestibular cochlear nerve (VIII)] glossopharyngeal nerve (IX), accessory nerve (XI) and hypoglossal nerve (XII).
The compression symptoms of trigeminal nerve, facial nerve, vestibular cochlear nerve, glossopharyngeal, accessory nerve and hypoglossal nerve are as follows; trigeminal neuralgia; facial spasm; dizziness accompanied with buzzing; residual feeling of fish bone on throat; leaning inclination of the face or neck: lingual atrophy on one side, respectively (3-5).
Trigeminal nerve includes three branches: ophthalmic, maxillary and mandibular branch nerves. The ophthalmic and maxillary nerves are purely sensory and the mandibular nerve has sensory and motor functions. The motor branch of the mandibular nerve controls the mastication muscles. The trigeminal nerve comes out of the lateral aspect of the upper pons and enters Meckel cave via the prepontine cistern, forming the semilunar ganglion (7). Trigeminal neuralgia is estimated to occur with the annual incidence of 0.4-2 per 10,000 people and usually begins in people over 50 years, with prevalence increasing with age (7-9). The maxillary branch is the most affected and the ophthalmic branch the least. Women are more affected than man (1.5 vs 1) (8, 9). Trigeminal nerve delivers feelings of the face and surface of the eye. Trigeminal neuralgia usually causes severe facial pain that lasts for a few seconds on the side of the affected nerve, in some cases the pain can last for minutes to hours and even become constant (8, 9). The responsible artery is most commonly the superior cerebral artery (4, 7-9). In our case, he suffered from painful right upper gingiva, indicating V2 area of trigeminal nerve areas. Compared time of flight MRI with balanced steady-state free precession (heavy T2WI) (10) right trigeminal nerve was confirmed to be compressed by right superior cerebellar branch artery.
【Summary】
We present a fifty one-year-old male suffering from right painful upper gingiva. MRI showed compression of right trigeminal nerve by right superior cerebellar branch artery. It should be in borne in mind that the transition site between central myelin sheath by oligodendrocyte and peripheral myelin sheath by Schwann cells is vulnerable to mechanical compression of brain branch artery. The transitional sites of brain nerves exist within 5 mm from brainstem except vestibular cochlear nerve whose transitional site is approximately 10 mm. The compression symptoms of trigeminal nerve, facial nerve, vestibular cochlear nerve, glossopharyngeal, accessory nerve and hypoglossal nerve are as follows; trigeminal neuralgia; facial spasm; dizziness accompanied with buzzing; residual feeling of fish bone on throat; leaning inclination of the face or neck: lingual atrophy on one side, respectively. The oculomotor nerve compression is arisen by aneurysm of posterior communicating artery and the medullary oblongata compression is done by elongation of vertebral artery, causing sagging eyelids & anisocoria and contralateral discomfort feeling or muscle weakness, respectively. In our case, he suffered from painful right upper gingiva, indicating V2 area of trigeminal nerve areas.
【References】
1.Peker S, et al. Microanatomy of the central myelin-peripheral myelin transition zone of the trigeminal nerve. Neurosurgery 2006;59:354–59; discussion 354–59
2.De Ridder D, et al. Is the root entry/exit zone important in microvascular compression syndromes? Neurosurgery 2002;51:427–33
3.Guclu B, et al. Cranial nerve vascular compression syndromes of the trigeminal, facial and vago-glossopharyngeal nerves: comparative anatomical study of the central myelin portion and transitional zone—correlations with incidences of corresponding hyperactive dysfunctional syndromes. Acta Neurochir (Wien) 2011;153:2365–75
4.Haller S, et al. Imaging of Neurovascular Compression Syndromes: Trigeminal Neuralgia, Hemifacial Spasm, Vestibular Paroxysmia, and Glossopharyngeal Neuralgia. American Journal of Neuroradiology August 2016;37:1384-1392
5.Deep NL, et al. Magnetic Resonance Imaging Assessment of Vascular Contact of the Facial Nerve in the Asymptomatic Patient. J Neurol Surg B Skull Base. 2016; 77: 503–509.
6.Ravikanth R, et al. Posterior communicating artery aneurysm presenting with ipsilateral oculomotor nerve palsy. TNOA J Ophthalmic Sci Res 2019;57:182-3
7.Nurmikko, TJ, et al. Trigeminal neuralgia—pathophysiology, diagnosis and current treatment. Pain; 2009 :87: 165–166.
8.Prieto R, et al. Trigeminal neuralgia: Assessment of neurovascular decompression by 3D fast imaging employing steady-state acquisition and 3D time of flight multiple overlapping thin slab acquisition magnetic resonance imaging. Surg Neurol Int. 2012;3 (1): 50.
9.Tash RR, et al. Trigeminal neuralgia: MR imaging features. Radiology. 1989;172 (3): 767-70.
2020.1.8