Moyamoya disease (MMD) is a group of occlusive diseases characterized by progressive stenosis or occlusion of the terminal internal carotid arteries and their large branch vessels bilaterally, with the formation of an abnormal neovascular network at the base of the skull. The name “smoke” comes from the fact that the cerebral angiogram shows a blurred reticular shadow at the base of the brain due to abnormal capillary hyperplasia, resembling a puff of smoke from smoking. The clinical manifestations are mainly divided into two categories: hemorrhage and ischemia, with a bimodal distribution of the age of onset between 5 and 40 years old, and ischemia as the main clinical manifestation in children, while ischemia and hemorrhage are basically the same in adult patients. The essence of the disease is occlusion of the arterial trunk at the base of the brain with compensatory vascular proliferation.
Disease Profile
Smoker’s disease, also known as anomalous vascular network at the base of the brain, is a group of cerebrovascular diseases characterized by narrowing or occlusion of the siphon of the internal carotid artery and the beginning of the anterior and middle cerebral arteries, and the appearance of an abnormal network of small vessels at the base of the brain. It is called smoky disease because the cerebral angiogram shows many dense piles of small vessels, resembling the smoke exhaled during smoking.
The disease was first described by Shimizu and Takeuchi in Japan in 1955 and named by Suzuki in 1966. It has been found in Chinese and Japanese as well as in Caucasians, Negroids, and Caucasians. According to the literature, the Chinese and Japanese are the most common.
Symptoms and signs
The onset of smoker’s disease is more common in children and adolescents, and often starts as a stroke, which can manifest as cerebral thrombosis, as well as cerebral hemorrhage and subarachnoid hemorrhage. Patients may present with varying degrees of hemiparesis or sequential paralysis on the right and left sides, which may be accompanied by aphasia, choking on water, dysphagia, mental retardation, dementia, seizures, headaches, and transient ischemic attacks.
Infarcts or hemorrhagic changes are usually seen on CT scans of the head. Infarcts are often multiple, with frontal, temporal, parietal, occipital, basal ganglia regions, and thalamus being the most common, and frontal lobe atrophy may be combined in half of the patients. The hemorrhage can be lobar hemorrhage, basal ganglia hemorrhage or subarachnoid hemorrhage, while high
The hemorrhage can be lobe hemorrhage, basal ganglia hemorrhage, or subarachnoid hemorrhage, while the hemorrhage caused by high blood pressure is mostly in the basal ganglia. Patients with cerebral hemorrhage may also have infarct foci and/or brain atrophy.
Cerebral angiography may reveal stenosis or opacification of the beginning of the internal carotid artery, the beginning of the anterior and middle cerebral arteries, and a large number of small vascular clusters in the basal ganglia, such as smoke from smoking. In addition, a compensatory branch of the collateral circulation can be formed in the brain. As the disease progresses, the number of compensatory anastomosing branches gradually decreases or shrinks.
Etiology of the disease
It should be noted that there is no relationship between smoky disease and smoking. Some scholars have found that mother and son or brother and sister in individual families can have similar disease, which is considered to be related to congenital factors. However, based on clinical, pathological, immunological and laboratory studies, most scholars believe that this is a group of occlusive cerebrovascular diseases that occur later in life and may be related to allergic cerebral vasculitis
Four types of clinical manifestations
The age of onset is mostly below 10 years old, with an average of about 4 or 5 years. Japanese cases are more common in girls, and no gender differences have been reported in China. The main symptoms are recurrent transient ischemic attacks (TIA), motor-sensory disturbances (transient hemiparesis or alternating hemiparesis), seizures (mostly partial, may be hemiparesis followed by hemianopsia, or HHE), headache, cerebral infarction, and mental deficits. Headache starts after 5 years of age. Mental retardation is seen in 65% of cases, mainly in those with a disease duration of more than 5 years.
Fukuvama et al. and maizunfi et al. believe that the disease can be divided into four clinical types, of which the TIA type accounts for the majority, while the epileptic type is often accompanied by the infarct type, and the hemorrhagic type is mainly seen in adults. the TIA type has a later onset, averaging 5.5 years, and has a better prognosis; the epileptic type or infarct type has an average onset between 1.5 and 2 years, and has a poorer prognosis.
1, TIA type: the most common, seen in about 70% of all idiopathic smog. The clinical characteristics are recurrent transient paralysis or weakness, mostly hemiparesis, or alternating right and left hemiparesis or double hemiparesis. There is complete recovery of motor function after an attack. The course of the disease is mostly benign, with a tendency to spontaneous remission or complete cessation of attacks. Very few cases are associated with hemiplegic attacks, headache or migraine. Rarely, there is transient sensory impairment, involuntary movement or mental retardation.
2. Infarct type: acute stroke resulting in permanent type of paralysis, aphasia, visual impairment and mental retardation.
3.Epileptic type: frequent seizures, partial seizures or seizure continuity with EEG epileptiform discharges.
4. Hemorrhagic type: subarachnoid hemorrhage or brain parenchymal hemorrhage, seen in older children and adult cases.
The last three types of the above clinical typing are called “non-TIA type”, which has a complex and variable course and a poor prognosis, and mostly manifests as a mixed type, such as epileptic type plus infarct type, epileptic type plus TIA type. In case of simple seizures, the prognosis is not necessarily poor. Regardless of the type, the prognosis is worse in those with onset before the age of 4 years. In addition, the clinical symptoms and their severity are determined by the compensatory effect of the collateral circulation. If adequate cerebral perfusion is maintained, there may be no clinical symptoms, or only transient TIA seizures, or headaches. If cerebral perfusion cannot be maintained, the symptoms are severe and cause extensive brain damage.
Diagnostic tests
1. Medical history Ask about any history of meningitis, leptospirosis, cranial infection, trauma or radiotherapy; any limb paralysis, aphasia, epilepsy, severe headache, fainting and impaired consciousness. Pay attention to the onset and duration of the disease.
2. Physical examination Any fundus edema, limb paralysis, aphasia and meningeal irritation signs.
3.Laboratory tests: Immunoreactivity of syphilis, leptospirosis and blood sedimentation in serum and cerebrospinal fluid, which can help to understand the cause of the disease.
4.Lumbar puncture In case of secondary subarachnoid hemorrhage, bloody cerebrospinal fluid can be seen.
5.Cerebral angiography See narrowing of the upper siphon of the internal carotid artery and the beginning of the anterior and middle cerebral arteries, smoky abnormal vascular network at the base of the brain and extensive formation of collateral circulation. It should be differentiated from cerebral atherosclerotic cerebral infarction and arteriovenous malformation, and is the most important examination.
6.CT scan In secondary cerebral infarction, hypodense areas with consistent vascular distribution can be seen. In cases of subarachnoid hemorrhage, increased density or hematoma formation can be seen.
Treatment options
The treatment of smoker’s disease has no ideal method at home and abroad because the cause of its pathogenesis is unknown. Internal medicine is based on symptomatic treatment with vasodilators and antibacterial agents, but the efficacy is not satisfactory. Although more than ten surgical procedures have been developed since the discovery of smog in Japan in 1961, the core of these procedures is to divert the external carotid artery into the skull. At present, international treatment of smog is mainly based on direct anastomosis of the superficial temporal artery-medial cerebral artery and indirect anastomosis of the EDAS.
Safety of medication
1.Pay attention to rest and functional exercise of paralyzed limbs.
2.Enhance nutrition and give high protein and high vitamin diet.
3.In case of subarachnoid hemorrhage, do not move the patient, avoid coughing, sneezing and holding the breath to defecate and other actions that increase the pressure in the chest and abdominal cavity.
4.Flooding should be prevented, rodents should be exterminated, poultry should be kept in captivity to prevent contamination of water sources, and drinking water should be disinfected.
5.Educate children not to drink raw water, not to play in infected water, bathing, etc., to avoid leptospirosis.
Reasons for misdiagnosis
Leptospirosis is easily missed or misdiagnosed clinically, and most patients experience a considerable period of time from the appearance of clinical symptoms to diagnosis, taking an average of two and a half years. Most patients are diagnosed with simple symptoms before diagnosis, and a few have been misdiagnosed with encephalitis, mitochondrial myeloencephalopathy, and gray matter heterotopia. There are several reasons why patients with smog are underdiagnosed or misdiagnosed.
1. The clinical symptoms of smog are complex and variable
Some symptoms of smog disease such as episodic limb numbness and weakness or paralysis of one limb are easily thought of as vascular disease, but certain symptoms are difficult to think of directly related to vascular lesions, such as blurred vision, headache, dizziness and vertigo, episodic disorders of consciousness, limb twitching or mental retardation, etc. Therefore, if clinicians lack sufficient knowledge of smog disease and do not arrange corresponding examinations related to cerebral artery lesions for patients, such as transcranial Doppler ultrasound (TCD), magnetic angiography (MRA) and digital subtraction angiography (DSA), etc., will lead to missed diagnosis.
2.Cranial CT and MRI do not always have abnormal changes
Many patients and even many doctors mistakenly believe that as long as the head CT or MRI is normal, there is no problem, but in fact, this is not true for the diagnosis of smog. The first lesions in smoker’s disease occur in the arterial ring at the base of the brain, and the arteries do not develop from stenosis to occlusion in a short period of time, but usually over a long period of time, from a few years to several decades. In addition, without experience or careful observation, clinicians may overlook the sparse vascularity of the large arteries at the base of the skull and the increase in vascular flow space at the base of the brain as shown on the T2 phase. Some physicians have repeatedly performed cranial CT and cranial MRI examinations on patients, but have not examined the cerebral arteries once, resulting in patients with milder symptoms of smog being undiagnosed for a long time.
3. Some patients with cranial MRI changes are easily confused with other diseases
After the gradual occlusion of the skull base arteries in patients with smoker’s disease, it leads to the formation of extensive intracranial and extracranial and cortical side branches, thus changing the blood supply range of each major cerebral artery. Therefore, in some patients, the foci of cerebral infarction do not match the distribution range of cerebral arteries, and are easily confused with encephalitis or mitochondrial myoencephalopathy. Such patients also often have many head MRIs but have not been examined for cerebral arteries.
4. Adult ischemic symptoms are easily labeled as cerebral atherosclerosis and cerebral thrombosis, and the cause of stroke is no longer sought.
When a stroke occurs in a child, it is easy to think about the cause of the stroke, but in adults with ischemic stroke, it is easy to conclude that cerebral arteriosclerosis and cerebral thrombosis are the cause of the stroke without looking into the cause, thus many adults with smog are missed.