Basilar impression
Basilar impression is a cranial pathology, which is manifested by the displacement of part of the occipital bone towards the junction of the upper cervical spine with the base of the skull. Clinical ones consist in the development of cranial nerve dysfunction, hydrocephalus, symptoms of spinal lesions in the upper cervical region, cerebellar disorders and other neurological symptoms against the background of cranial displacement of the spine and a decrease in the volume of the skull. Basilar impression may be congenital or have an acquired character of development. The symptoms of this pathology are associated with compression of the brain stem, cranial nerves and the upper neck of the spinal cord.
The content of the article:
Causes of basilar impression
Symptoms of basilar impression
Diagnosis of basilar impression
Treatment of basilar impression
Basilar impression
Causes of basilar impression
Since this pathology can be both congenital and acquired, the factors contributing to its development have the same classification. In the first case, the cause of pathology is considered to be various hereditary diseases, which are often combined with other craniopathologies. The most diagnosed combined defects are a combination of congenital platybasia and basilar impression. Often, the mechanism of development of congenital basilar impression is triggered as a result of harmful effects on the fetus during intrauterine development. Such influences include radiation exposure of a pregnant woman, contact of a pregnant woman with various chemicals, infectious diseases during the first three months of pregnancy, etc.
The acquired form of this pathology occurs against the background of structural disorders of bone elements in the occipital region, which develop as a result of osteoporosis, the cause of which, as a rule, are diseases such as rickets (severe form), osteomalacia, hypoparathyroidism, Paget’s disease, etc. In addition, the cause of the acquired form of basilar impression may be pathological changes in the occipital bone as a result of brain tumor lesions, birth injuries, calcium metabolism disorders in various concomitant pathologies, as well as inflammatory processes accompanying various infections.
Symptoms of basilar impression
According to the data obtained during the study of this disease, as a rule, the first clinical manifestations do not occur before adolescence. Most often, this pathology is detected in people aged fifteen to twenty years, sometimes there are cases of its detection in patients under the age of thirty years.
Painful sensations
A decrease in the volume of the posterior cranial fossa and dysfunction of the cerebrospinal circulation provoke an increase in intracranial pressure, which entails the appearance of bursting headaches in the occipital region. In the process of gradation of intracranial hypertension, pain sensations spread to the entire head, along with them there is a feeling of pressure from inside the eyes.Headache may be accompanied by the phenomena of vegetative symptoms, in particular, an increase in blood pressure, a feeling of heat, sweating, palpitations, etc. In the case of a prolonged increase in intracranial pressure, during the examination of the fundus by ophthalmoscopy, congestion in the optic nerves is diagnosed. Also, pain is often localized in the cervical spine and upper extremities, which is caused by compression of the nerve endings of the spinal cord.
Subjective feelings
There may be a feeling of itching or crawling goosebumps in these areas. There is a decrease in the mobility of the cervical spine.
Among other subjective sensations of patients, dizziness, unsteadiness when walking and instability are noted. Some patients are diagnosed with double vision, which most often occurs when looking down. During examination, nystagmus (involuntary eye oscillation) is visualized.
With compression of the cranial nerves, choking, difficulty breathing, voice changes, hearing loss, impaired sensitivity on the face may occur. Sensorineural hearing loss is detected by audiometric examination. In addition to other neurological symptoms, compression of the spinal structures may develop, which sometimes leads to limited mobility of the upper and lower extremities.
One of the characteristic features of this pathology is a short neck and a low level of hair growth, which are well visualized during the diagnostic examination of the patient.
Diagnosis of basilar impression
This diagnosis is made by analyzing all the data obtained as a result of neurological examination, laboratory, instrumental studies, as well as CT, MRI or radiography of the brain and upper cervical spine. If there is evidence of pathology, the patient is shown to conduct a number of specific studies, which include:
MacGregor’s method: consists in the fact that on an MRI median sagittal projection or lateral craniogram, the lowest point of the scales of the occipital bone and the posterior edge of the hard palate are connected. With basilar indentation of the bone structures of the skull, the presence of a tooth-like process standing above the MacGregor line by more than 8-10 mm is noted.;
Chamberlain’s method: in the same images, as in the study of the skull using the MacGregor method, the posterior edge of the large occipital foramen and the posterior point of the hard palate are connected. The normal location is the edge of the tooth-like process of the second cervical vertebra lower in relation to this line;
The size of the sphenoidal angle: measured between the slope and the plate of the pterygoid bone. A sign of a basilar impression will be the size of this angle over 1300;
The slope of the occipital bone: with a basilar depression is no more than 30 mm;
The Klaus height index is determined by connecting the inner occipital protuberance with the back of the Turkish saddle. A perpendicular is drawn to this line relative to the apex of the dentoid process. The resulting distance should normally be greater than 35 mm.
If the information content of the images obtained by the standard method is low, several more images with functional tests are performed, during which the patient is asked to bend and unbend the neck. The data obtained make it possible to identify the basilar impression with greater accuracy. In addition, these studies allow us to determine intracranial hypertension and complications that may develop against its background. Ophthalmoscopic examination allows to confirm intracranial hypertension.
Sometimes, with minor deviations from normal indicators, the basilar impression is detected randomly, during an X-ray examination of the head. Often such deviations may not have clinical manifestations. In the absence of symptoms of the disease and minimal deviations in the structure of the skull bones, dynamic observation is recommended.
To make a correct diagnosis, differential diagnosis is important, the purpose of which is to exclude other pathologies with similar symptoms:
Pierre-Marie’s ataxia;
cortical type of ataxia;
neoplasms of the cerebellum;
Friedreich’s ataxia.
Treatment of basilar impression
The tactics of treatment of basilar impression depends on the degree of clinical manifestations of pathology. With minor and not pronounced symptoms, treatment is not applied, such patients are recommended to be under dynamic supervision, for this they should regularly visit a neurologist and undergo routine examinations.
With the steady progression of symptoms, patients are shown surgical treatment. Also, indications for surgical treatment may be symptoms of compression of the cerebellum, spinal cord, brain stem or manifestations of pronounced cerebrospinal fluid dysfunction in combination with occlusive syndrome. The expediency of surgical methods of treatment is determined by a neurologist. To reduce the compression of the structures of the brain and spinal cord during the operation, the large occipital foramen is expanded. The operation is performed under anesthesia, after preliminary preoperative preparation of the patient. In addition, there is provided drug therapy aimed at normalization of cerebrospinal fluid dynamics.
