Basilar impression is a congenital or acquired indentation of the part of the occipital bone into the cranium in the area of the craniovertebral transition. The decrease in the volume of the skull and cranial displacement of the spine that develops with this pathology are considered to be the cause of the development of cerebellar disorders, hydrocephalus, disorders in the functioning of the cranial nerves, radicular symptom and damage to the cervical zones of the spinal cord. The disease is diagnosed by radiography of the craniovertebral junction, MRI and CT of the skull and cervical spine. This disease is treated exclusively by surgery.
Pathology Description
Basilar impression has a funnel-shaped impression of the depression of the slope of the occipital bone with a deepening of the edges of a large opening into the skull. These disorders lead to a displacement of the spine to the brain and a decrease in the volumes of the posterior fossa of the skull. The tooth-like process of the second vertebra is localized in the region of the occipital foramen or slightly above it in the cranial cavity.
In neurology, this pathology refers to defects of the craniovertebral transition, which also includes the assimilation of atlant, platibasia, Chiari anomaly and atlantoaxial dislocation. Often, congenital pathology is combined with other malformations of the spine and craniovertebral anomalies. In most cases, a combined defect is observed in which there is a combination of congenital platybasia and basilar impression.
The main causes of the disease
Primary (congenital) basilar impression develops in the prenatal period. It is due to a genetic predisposition, as well as negative effects during pregnancy on the fetus. Factors contributing to the development of such defects include maternal diseases and infections that she suffered during pregnancy (chlamydia, measles, rubella, cytomegalovirus infection, etc.), contact with chemicals, and radiation.
Secondary type
Secondary (acquired type) basilar impression occurs as a result of a violation of the bone structures of the occipital bone. The cause may be osteoporosis, severe rickets, osteomalacia, hypoparathyroidism, Paget's disease. Acquired impression is possible due to destructive changes in the nape bone during germination of a cranial fossa tumor or due to an inflammatory process (tuberculosis, syphilis, osteomyelitis, actinomycosis).
Symptoms of the disease
Consider the symptoms. Basilar impression is characterized by the first symptoms under the age of 25 years, most often in the period from 10 to 20 years. Clinical manifestations of this pathology occur due to a decrease in the posterior cranial fossa, which leads to an increase in the level of intracranial pressure, compression of the cerebellum, roots of the cranial and cerebral nerves, brain stem, and hydrocephalus. In addition, cervical segments are compressed, which leads to the development of spinal and radicular symptoms.
Common symptoms of basilar impression are reduced to cephalgia in the occipital region, often having a paroxysmal character and depending on the position of the head. Against the background of pain in the head, vegetative disorders are possible: a sense of anxiety, tachycardia, hyperhidrosis, a decrease in blood pressure. In some cases, there is unilateral pain in the back of the head. Occasionally, it spreads to the eyes.
Cerebellar symptoms
Cerebellar symptoms are the development of ataxia - impaired coordination and gait. Damage to the brain stem causes nystagmus, hoarseness, hearing loss, dizziness, and skin sensitivity disorders. These symptoms are most pronounced in cases where the disease is combined with assimilation of the atlas.
Often with basilar impression, there are pains in the upper limbs and neck, as well as paresthesia (numbness) in this area. Such phenomena are due to compression of the roots of the cervical spine.
When examining patients suffering from basilar impression, there is often a short neck, a low hairline, shakiness when taking the Romberg pose, oversight during coordinating tests, decreased sensitivity on the face and in the neck cervical dermatomes.
Platibasia
This pathology is an anomaly in the structure of the skull, which is characterized by its flatter base than with a normal structure. Platibasia is the most common defect that accompanies basilar impression. It has a congenital or acquired character. Clinically, pathology is manifested in a flattening of extreme severity or its combination with other craniovertebral anomalies. For a correct diagnosis, it is often enough to have a x-ray of the skull in lateral projections, but in some cases it is necessary to prescribe an MRI of the brain, CT of the skull, radiography or CT of the cervical area. With mild or no clinical symptoms, platibasia does not need treatment. Surgery is possible with a combination of pathology with severe symptoms, and it comes down to an increase in the large occipital foramen in size.
What is the danger of basilar impression?
This pathology has a predominantly favorable prognosis for both human life and recovery. Such pathology does not have independent complications and consequences, which is caused by the absence of any neurological disorders.
Diagnosis of this disease
The patient’s complaints, the history of their development (history of pathology), and the results of a neurological examination, prompt a neurologist to suggest the presence of this disease and anomalies in the area of the craniovertebral transition and cranial fossa. In this case, in order to diagnose basilar impression or another anomaly of this category, an X-ray examination is first of all carried out. The best visualization of the structures of this area, as well as information on other malformations with which congenital type basilar impression is often combined, can be obtained using CT of the spine and skull.
Sighting radiography of the craniovertebral transition zone and the spine in the cervical region are carried out in the face (direct) and profile (lateral) projections. Pathology is diagnosed by an increase in the angles between the slope and the bone plate of more than 130 °, as well as by the shift of the process of the second vertebra up. The location of this process is determined in relation to the conditional lines: Chamberlain and the line de la Petit. Normally, the process of the second vertebra is below such lines. During basilar impression, the process is displaced 6-30 mm upward from the Chamberlain line and 11-15 mm from the de la Petit line.
When conducting ophthalmoscopy in patients with basilar impression, congestive optic nerve discs can be determined, while performing threshold audiometry, a sensorineural type of hearing loss. To determine the state of soft tissue structures of the spinal cord and cranial fossa, to assess the degree of pressure on them during basilar impression, it is recommended to conduct an MRI of the spine and an MRI of the brain.
With basilar impression, a differentiated diagnosis of other defects of the craniovertebral transition is required. As well as Frdreich ataxia, Pierre-Marie-type ataxia and cortical ataxia.
Basilar Impression Treatment
In cases where this pathology is an accidental finding after an X-ray examination and does not cause symptoms of compression of the brain structures, therapy is not required. An indication for surgical intervention in basilar impression is the steady progression of clinical symptoms; signs of pressure on the spinal cord, brain stem, or cerebellum; significant cerebrospinal fluid disorders with increasing signs of occlusion syndrome. In order to decompress during the surgical treatment, an expansion of the occipital foramen is performed.
Reviews on basilar impression from patients
In the reviews, patients with this anomaly of an acquired or congenital nature indicate that this disease most often causes the development of severe headaches, constant dizziness, visual impairment and other signs of compression of the structures of the head. At the same time, treatment is carried out by an operative method and, according to patients, is a very complex surgical event. Nevertheless, after him, patients felt good, and they did not show signs of basilar impression. So the forecasts are favorable.
We examined the symptoms of basilar impression. Why it is dangerous is now clear.