Neurovascular conflict is defined as compression of a nerve by a blood vessel. Most often the vessel causing the nerve irritation is an artery running in close proximity to the nerve, less often a vein. Variations in the volume of the vessel caused by varying blood flow can irritate the nerve, causing destruction of its myelin sheath and damage to the nerve itself, generating abnormal excitations in the nerve.
Not all cases of neurovascular conflict produce clinical symptoms.
Its clinical manifestations have been documented in a case:
- trigeminal neuralgia,
- lingual-pharyngeal neuralgia,
- ganglion neuralgia of the knee,
- hemifacial spasm.
Neurovascular conflict can also involve other cranial nerves: accessory nerve, sublingual nerve, block nerve, inversion nerve or oculomotor nerve, but these cases are very rare.
Trigeminal neuralgia
It is characterised by sudden, unilateral, piercing pain lasting a few seconds in the face, in the area of the trigeminal nerve innervation. The neuralgia can affect one, two or all three branches of the trigeminal nerve. It is most commonly located in the area of the second and third branches of the nerve. The discomfort is so severe that it can make it impossible to speak or eat. The characteristic feature is the presence of trigger points, which, even slight irritation - speaking, biting, brushing teeth, light touch or even a breath of wind - causes an onslaught of pain. The pain is paroxysmal in nature, with symptoms usually lasting from a few seconds to a few minutes, with a frequency ranging from several per day to several per month. Neuralgia does not cause objective abnormalities found on neurological examination.
Only some cases of trigeminal neuralgia are caused by neurovascular conflict. In such cases, once it is confirmed by imaging studies, surgical treatment can be applied - suboccipital craniectomy and microsurgical decompression of the nerve (Janetta operation). The most common vessel causing conflict in trigeminal neuralgia is the superior cerebellar artery. In addition, the conflict may be caused by the inferior cerebellar artery or a venous vessel.
Other cases of neuralgia are spontaneous neuralgia, the aetiology of which remains unclear, or symptomatic in the course of multiple sclerosis, aneurysm, tumour of the temporal bone pyramid or sternocerebellar angle, among others. In spontaneous trigeminal neuralgia, the treatment of choice is pharmacotherapy. The most effective antiepileptic drugs are carbamazepine, oxcarbamazepine, phenytoin, clonazepam, lamotrigine, pregabalin, gabapentin, topiramate or valproic acid. Baclofen in doses of 10-50mg daily is also used in treatment, but has less efficacy compared to antiepileptic drug therapy. In cases refractory to pharmacotherapy, surgical techniques may be considered: balloon compression of Gasser's ganglion, thermocoagulation, Gamma Knife therapy, glycerolysis, local analgesia with opioids or cryoanalgesia.
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Lingual-pharyngeal nerve neuralgia
In the course of lingual-pharyngeal neuralgia, pain is located unilaterally in the area of the posterior pharyngeal wall, palate, palatine tonsils, base of the tongue, angle of the jaw, depth of the external auditory canal or mastoid process. It has a burning or stabbing character. Pain attacks, as in trigeminal neuralgia, are unilateral, brief ( 10sec - 2 minutes ) and triggered by irritation of the trigger zones. Trigger points are located in the amygdala, ear canal, scaphoid and contralateral ear. Seizures can provoke activities such as speaking, chewing, yawning, coughing or swallowing and occur with a frequency of several per day to one every few weeks. Reflex bradycardia and syncope due to stimulation of the vagus nerve nucleus by discharges in the lingual-pharyngeal nerve nucleus occur. The treatment for lingual-pharyngeal neuralgia with an imaging-confirmed aetiology of neurovascular conflict is microsurgical decompression.
Ganglion neuralgia
Ganglion neuralgia of the knee is caused by irritation of the intermediate nerve. Apart from cases caused by a neurovascular conflict, this neuralgia can occur spontaneously - without any identifiable cause or in the course of a herpes or herpes virus infection. The pain is paroxysmal, unilateral and of short duration. It is felt in the temple, mastoid process, auricle, external auditory canal and angle of the jaw.
Hemifacial spasm
Hemifacial spasm manifests as attacks of involuntary clonic or tonic contractions of the facial muscles innervated by the facial nerve. In the classic form of hemifacial spasm, the spasms start in the orbital region - the eyelid muscles, usually with spasms of the lower eyelid. In the atypical form, which occurs in about 10% of patients, the first spasms appear in the mouth area. This is followed by the other muscles of the midface innervated by the facial nerve - frontalis, oculomotor, angular, zygomatic, laughter and wide neck muscles. Symptoms are exacerbated during stressful situations, fatigue, facial movement, but can also occur during sleep. Paroxysms of hemifacial spasm cannot be consciously stopped. The duration of contraction, rhythm and degree of facial muscle involvement varies from patient to patient. Approximately 30% of patients have a slight paresis of the lower facial muscles after several years of illness. The spasm may be accompanied by autonomic symptoms such as epiphora. The vessels that cause neurovascular conflict with the facial nerve leading to hemifacial spasm may be the dolichoepithelial basilar artery, the inferior cerebellar artery, the inferior cerebellar artery, the vertebral artery or venous vessels.
