Moyamoya disease is a rare vascular disease, which is a slowly progressive stenosis of the intracranial cerebral arteries, accompanied by the development of bypass collaterals. It is clinically manifested by symptoms of chronic cerebral ischemia, TIA, subarachnoid hemorrhages, ischemic and hemorrhagic strokes. When making a diagnosis, the main data are cerebral angiography. Additionally, EEG, MRI /CT of the brain, ophthalmoscopy are performed. Treatment may be conservative, but the most effective operation is to impose extracranial microanastamosis.
I67.5 Moyamoya disease
Moyamoya disease is a rare pathology of cerebral vessels, described in detail by Japanese clinicians Kudo and Takeuchi. Until 1962, it was considered characteristic exclusively for the Japanese, then information about its ubiquity began to appear. Moyamoya disease is more common in Asians. Its prevalence in Japan is 3.5 cases per 1 million population, in the USA it does not exceed 1 case per 1 million.
The disease got its memorable name due to the characteristic angiographic picture. The term was introduced into practical neurology in 1967 by Suzuki and Takaku. Translated from Japanese, it means “like cigarette smoke.” Moyamoya disease can manifest in 2 age periods: up to 10 years of age (on average 5 years) and in the period from 30 to 40 years. Women get sick about 1.5-2 times more often than men.
The basis of the disease is a gradually increasing narrowing of the lumen of the intracranial part of the internal carotid artery, separate sections of the middle and anterior cerebral arteries. Morphological changes detected in the affected segments of the carotid artery and arteries of the Willis circle are characterized by intimal fibrosis and its expansion, thinning of the middle layer of the vascular wall. As a result, stenosis or vascular occlusion is formed. The process is accompanied by the development of a network of collateral vascular anastomoses providing alternative blood supply to the brain. Over time, the internal carotid arteries are completely occluded, the cerebral blood supply occurs only thanks to the collaterals developed from the external carotid and vertebral arteries.
These factors remain unclear. It is assumed that abnormalities of cerebral vessels are genetically determined. In 1999, a DNA analysis of 16 families with this pathology was carried out, which revealed the presence of a gene mutation at the 3p26-p24.2 locus. However, in practice, the sporadic nature of the disease was determined in most patients. On the other hand, according to angiography, a large number of familial subclinical (latent) forms have been diagnosed.
According to another hypothesis, moyamoya disease is a nonspecific arteritis resulting from autoimmune reactions and provoked by inflammatory processes. According to some data, about 70% of cases of the disease are associated with sinusitis, chronic tonsillitis, otitis media. In addition, the literature describes combinations of moyamoya disease with other various diseases: tuberous sclerosis, Recklinghausen neurofibromatosis, sickle cell anemia, Hirschsprung’s disease, leptospirosis, Marfan syndrome, Apert syndrome, traumatic brain injury.
Clinical manifestations are associated with two pathogenetic mechanisms: progressive chronic cerebral ischemia and hemorrhages from dilated and thinned collateral vessels. As a rule, the ischemic mechanism is more pronounced in children, and hemorrhagic in adults.
In childhood, moyamoya disease debuts with transient ischemic attacks. Ischemic paroxysm may be accompanied by a transient speech disorder (dysarthria, motor aphasia), hemiparesis or weakness of only one limb, sensory disturbances, visual impairment. The occurrence of paresis on one side or the other of the body is characteristic. Possible epiprimes leading to the development of oligophrenia.
Adults often have periodic or persistent headaches, sometimes imitating migraines. They may be accompanied by tinnitus. Some patients complain of numbness of the limbs. Most patients have subarachnoid hemorrhages. The clinical picture and neurological status data are non-specific. Neurological examination can reveal asymmetry of nasolabial folds, pyramidal insufficiency in mono- or hemitype, mild coordination disorders, nystagmus, etc.
The danger of the disease lies in its main complication — an acute violation of cerebral circulation, which can occur according to the type of ischemic stroke or hemorrhagic stroke. Strokes can occur repeatedly, lead to disabling neurological deficits and to a fatal outcome.
In the anamnesis of patients, there may be indications of past episodes of ONMC. However, based on anamnesis and clinical picture, a neurologist cannot establish a diagnosis. Additional examinations and differential diagnosis with atherosclerosis of cerebral vessels, vasculitis, arteriovenous malformations, thrombosis, migraine with aura, intracerebral tumor, etc. pathology are needed.
An ophthalmologist is consulted with visiometry, perimetry and fundus examination. Loss of visual acuity, hemianopia, and other disorders may be diagnosed. Retinovascular changes and enlargement of the optic disc are visualized on the fundus during ophthalmoscopy. The EEG registers pathognomonic changes for moyamoya disease: after hyperventilation, the second phase of slow high-amplitude waves (the so-called re-build-up phenomenon) is recorded after 20-60 seconds. Due to the specificity of this phenomenon, EEG can be used as a screening diagnostic method.
In many patients, a CT scan of the brain visualizes small areas of reduced density in the cerebral substance. MRI allows you to verify them as focal infarcts. REG reveals a decrease in cerebral blood flow. The ultrasound of the vessels of the head determines the occlusion of the internal carotid artery. The gold standard in diagnosis is angiography. Confirmation of the diagnosis is the presence on the basis of the brain of an angiographic picture of a “ball of smoke released from a cigarette”. According to the angiography data, there are 6 stages of the disease: from partial narrowing of the distal part of the internal carotid artery to its absolute disappearance. Currently, vascular CT and MRI of cerebral vessels have become an alternative to X-ray contrast cerebral angiography. These methods are more accurate and less invasive.
Treatment and prognosis
Conservative treatment includes vascular (vinpocetine, nicergoline, nifedipine) and neurometabolic (gamma-aminobutyric acid, pyritinol, piracetam, hopanthenic acid) therapy. It can improve the clinical situation, but it is not able to stop the progression of the disease. A more radical method of treatment is surgery with the formation of a vascular shunt carrying blood bypassing stenosed arteries. It can be performed in a direct way with the suturing of the shunt to the vessels and indirect, in which the vascular shunt is placed on the surface of the brain. With the direct method, a sufficient level of blood supply is achieved immediately, with the indirect method, its development takes from 6 months to a year. Experience has shown significantly greater efficiency of direct bypass surgery. Ischemic episodes after its implementation occur only in 10% of patients, while after indirect bypass surgery they are noted in 56% of cases. Therefore, the standard in treatment is the technique of applying extra-intracranial anastamosis.
The prognosis with timely surgical treatment is mostly favorable. The average efficiency of the operation is estimated at 84%. There is a direct dependence of the effectiveness of treatment on the angiographic stage. In favorable cases, a significant regression of clinical manifestations is observed immediately after the treatment. Without treatment, the increasing deterioration of cerebral hemodynamics leads to a progressive neurological deficit, the occurrence of hemorrhagic and ischemic strokes. Among adults, the mortality rate is 10%, among children — 4.3%.