Microgyria is a rare form of cortical dysplasia, for which it is typical to reduce the size of the convolutions of the cerebral cortex (CC) with an increase in their total number. The disease occurs due to monogenic anomalies, intrauterine neuroinfections, and other congenital structural diseases of the central nervous system. Microgyria is manifested by intellectual disorders, convulsive seizures, disorders of motor function. For diagnostic purposes, a cerebral MR scan, an EEG, and a psychiatric examination are performed. Treatment includes anticonvulsants, neuroprotectors, rehabilitation with the participation of speech therapists, correctional teachers, kinesiotherapists.
ICD 10
Q04.3 Other reduction deformities of the brain
General information
Microgyria, which has the second name “congenital bilateral perisilvium syndrome”, is extremely rare, therefore, in modern neurology there is not a sufficient number of observations to identify the epidemiological features of the disease. Pathology has a variety of clinical symptoms, determined by the severity, localization of changes, as a result of which it can remain undiagnosed for a long time. Often microgyria is combined with pachygyria — flattening of the cortical gyri of the large hemispheres.
Causes
Most cases of pathology are congenital in nature: they are formed in the period of intrauterine development of the fetus under the influence of adverse factors. Although today the exact etiological structure of the disease has not been established, scientists distinguish several groups of predisposing factors:
- Genetic anomalies. The most studied defect of the SRPX2 gene, which is responsible for the formation of speech function, promotes the formation of new neuronal connections. The cause of the disease may be mutations PAX6, TBR2.KIAA1279, RAB3GAP1, COL18A1, deletion of the long arm of the 22nd chromosome.
- Congenital neuroinfections. Cytomegalovirus remains the main risk factor among intrauterine infections. The most severe cases are observed with the primary infection of the mother during pregnancy, which is why she does not have time to develop antibodies, and the virus quickly attacks the nervous system of the fetus.
- Porencephaly. Ischemic zones of nervous tissue can form around porencephalic cysts, which leads to partial wrinkling, flattening of the cortical convolutions. The probability of microgyria increases with large-sized cavities.
Pathogenesis
The convolutions of the brain are folds of gray matter on the surface of the large hemispheres, located between the depressions (furrows). They increase the volume of nervous tissue in the cranium with a relatively small size of the skull. Normally, differentiation of the layers of the cerebral cortex begins at the 6th month of intrauterine development, and by 8-9 months secondary, tertiary gyri are actively formed.
The appearance of congenital microgyria is often associated with abnormal migration of neurons, as a result of which the normal architectonics of the nervous tissue is disrupted, the size, structure, and sequence of convolutions change. In the secondary form of the disease, vascular disorders play an important role, leading to displacement of the nervous tissue, flattening of the relief of individual sections of the CC.
With microgyria, various variants of structural lesions of the cortex with heterotopy of gray matter are possible, combined with anomalies of other brain zones: hypoplasia or aplasia of the corpus callosum, transparent septum, abnormalities of the cerebellum, brain stem. The most common localization of microhyric changes is the area around the Sylvian sulcus separating the temporal lobe of the cortex from the frontal and parietal zones.
Symptoms
Signs of the disease appear more often in children, but can manifest at any age period. The classic manifestation of pathology is considered to be convulsive seizures, occurring in the type of generalized paroxysms with loss of consciousness, convulsions of the whole body or as partial episodes that last several seconds, at first go unnoticed. Seizures occur out of connection with provoking factors.
The second typical symptom of cortical dysplasia is motor disorders determined by the volume and localization of the affected area. The most common is central spastic hemiplegia — paralysis of one half of the body on the side opposite to the pathological focus, or diplegia — a bilateral lesion with a predominant decrease in the motor function of the lower extremities.
The third characteristic symptom of microgyria is mental retardation, in most cases observed already in early childhood. Parents notice that the child starts to sit and walk late, does not know how to speak at 2-3 years old, does not understand the speech addressed to him, is not interested in educational games. As the condition progresses, emotional instability, isolation, infantile behavior increases.
Complications
A complicated variant of microgyria is noted when the disease is combined with other types of cortical dysplasia, especially with agyria — the complete absence of convolutions in a certain area of CC, schizencephaly or porencephaly, focal transmantial dysplasia. In this case, a deep neurological deficit, a lag in psychomotor development, which has an irreversible character, are expressed from birth.
Mental retardation of moderate or severe degree provokes serious violations of the training and socialization of patients, causes the impossibility of independent living, disposal of material goods. Patients receive disabilities, they need the help of relatives and competent medical care, especially with severe mental retardation, which manifests itself as complete incapacity.
Diagnostics
Examination of patients with suspected microgyria is within the competence of a neurologist, according to the indications, a psychiatrist, a neurosurgeon is involved in the diagnosis. The initial consultation begins with clarifying complaints, assessing the time and nature of the appearance of symptoms, identifying the features of the course of the intrauterine, early neonatal period. The following examination methods are used to make a diagnosis:
- MRI of the brain. Neuroimaging is the main way to confirm the diagnosis of microgyria. According to the results of MRI, a decrease in the size of the cortical gyri in the area of the sylvian sulcus or other areas of the brain is determined, there may also be cracks or cysts of cerebral matter, areas of impaired blood flow, areas of necrosis or ischemia.
- Electroencephalography. EEG is performed in the presence of convulsive seizures against the background of microgyria to find foci of epileptic activity, to detect typical signs in the form of “acute-slow wave” complexes, high-amplitude acute waves.
- Psychiatric counseling. To diagnose the presence and severity of mental retardation, a psychiatric examination is necessary to collect complaints and anamnesis, evaluate the results of instrumental visualization, provide testing, and experimental psychological research.
Treatment
Cortical abnormalities are not amenable to etiopathogenetic treatment, so the only option available to patients is symptomatic supportive therapy. To eliminate epileptic seizures in microgyria sufferers, an individual course of anticonvulsants is prescribed, and behavior correction is performed with the help of tranquilizers, neuroleptics. Neuroprotectors and neurometabolic drugs are used to stimulate cognitive development.
The presence of pronounced cognitive impairments makes it necessary to carry out comprehensive rehabilitation measures for the maximum possible adaptation of such patients. Kinesiotherapists, clinical psychologists, correctional educators are involved in the treatment. The therapy program may include the following areas:
Neurocorrection. Work with defectologists according to a personalized scheme based on the neuropsychological characteristics of the patient, taking into account the “resource” sides of his psyche. Provides the development of motor skills, visual-motor coordination, the formation of the functions of concentration, thinking, memory.
Special training program. Patients with a mild degree of mental retardation in some cases study in general education institutions, the rest require classes in inclusive classes, which are based on concrete visual training, mastering elementary labor skills.
Psychological help. Patients with mental retardation have an unstable psyche, which is aggravated by problems with social adaptation, difficulties in communicating with others. Neuropsychologists are involved to solve these issues.
Prognosis and prevention
The prognosis in patients with microgyria is determined by the severity of neurological deficit, the presence of concomitant central nervous system abnormalities, the timeliness and completeness of medical care provided. Given the organic nature of the pathology, it is not possible to completely eliminate the symptoms, however, drug treatment in combination with rehabilitation programs significantly improves the quality of life of patients.
The possibilities of preventing microgyria are limited due to the ambiguity of the etiopathogenesis of the disease. The main method is to prevent infection with cytomegalovirus in pregnant women. To reduce the risk of other congenital anomalies that accompany microgyria, rational management of pregnancy and childbirth, the exclusion of teratogenic effects is necessary.