Basilar depression

Introduction to skull base depression The skull base sag (basilarinvagination) is a common clinical abnormality of the nervous system. This disease is a skull base tissue, axillary vertebrae and abaxial bone development malformation centered on the occipital foramen. The atlas is plunged into the cranial cavity. The vertebral dentate process is higher than the normal level into the occipital foramen, which makes the occipital foramen stenosis and the posterior fossa become smaller, thereby compressing the medulla, cerebellum and pulling the nerve root to produce a series of symptoms. At the same time, there may be insufficient blood supply to the vertebral artery. which performed. basic knowledge The proportion of illness: 0.001% Susceptible people: no special people Mode of infection: non-infectious Complications: cerebellar tonsil mandibular malformation hydrocephalus syringomyelia rickets osteogenesis imperfecta

The cause of skull base depression

(1) Causes of the disease

The main cause of basilar invagination is congenital bone dysplasia. Because of the earliest closure of the occipital occipital region in embryogenesis, congenital malformation is likely to occur in this area. Can be secondary to other diseases.

Hadley divides the disease into two types, namely:

1 congenital type: also known as primary skull base depression, accompanied by sacral occipital fusion, occipital bone flattened, occipital large hole deformation, odontoid upward displacement or even into the occipital foramen, resulting in occlusion of the occipital bone hole diameter, At 2 to 3 weeks of embryonic development, due to local defects in the embryonic segmentation, the atlas has entered the occipital foramen to varying degrees, sometimes with it. In recent years, it has been found that the disease is related to genetic factors, that is, the same family of siblings. There are several people who can develop the disease.

2 follow-up hair: also known as acquired skull base depression, less common, often secondary to osteitis, osteogenesis imperfecta, rickets, osteomalacia, rheumatoid arthritis or hyperparathyroidism, etc., leading to the skull base The bones become soft and the soft skull base is invaginated by the cervical vertebrae. The occipital cavities are elevated, sometimes reaching the tip of the rock, and becoming funnel-shaped. At the same time, the cervical vertebra is also inserted into the skull base, in order to adapt to the atlas. In the posterior arch, there may be crypts behind the large hole of the pillow, and the posterior arch of the atlas does not merge with the occipital bone.

(two) pathogenesis

Skull base depression causes stenosis of the occipital foramen, the posterior fossa becomes smaller, the medulla oblongata is compressed, the cerebellum and the traction nerve root produce a series of symptoms, and the vertebral artery compression combined with the lack of blood supply.

The pathological changes are as follows: the occipital macropore deformity includes the occipital basal part, the lateral part and the ankle dysplasia, causing the skull base to sag inward, the distance between the atlas and the occipital bone is shortened, the occipital occipital fusion, the atlas pillowization, etc. Also combined with atlantoaxial deformity, lamellar crack or absent, abnormal curvature of the craniocerebral transition.

The skull base depression is the most common malformation in the large occipital region. More than 90% of the skull base depression is the deformity of the occipital and atlantoaxial. The base of the occipital bone, the ankle and the scale are plunged into the cranial cavity with the occipital foramen as the center. The edge of the large hole has a shorter distance of the atlas, even with the posterior arch of the atlas, the occipital condyle is poorly developed, asymmetrical, the base of the occipital bone becomes shorter, straight, uneven, the base of the skull is funnel-shaped, and the atlas protrudes into the skull. The odontoid process of the vertebral column is higher than normal and enters the occipital foramen. The occipital foramen is shortened before and after, and the posterior cranial fossa is shortened, thereby compressing the medulla, cerebellum and pulling the nerve root, resulting in a series of neurological symptoms and signs.

In addition to the above-mentioned bone changes, local soft tissue can also produce thickening and contraction, fascial ligaments near the occipital macropores, dura mater, arachnoid adhesions, thickening, banding, thereby compressing the cerebellum, medulla, and cranial nerves The upper cervical spinal cord, the cervical nerve and the vertebral artery, etc., produce symptoms, and cerebrospinal fluid circulation disorder often occurs in the late stage, resulting in obstructive hydrocephalus and increased intracranial pressure.

Skull base depression often combined with cerebrospinal and other soft tissue malformations, such as cerebellar tonsil, syringomyelia and arachnoid adhesions.

Skull base depression prevention

Mainly pay attention to women during pregnancy, perinatal health and disease prevention and can not use drugs at random to prevent the birth of congenital malformations.

Skull base depression complications Complications cerebellar tonsil mandibular malformation hydrocephalus syringomyelia rickets osteogenesis imperfecta

Primary often combined with other malformations, such as flat skull base, midbrain aqueduct, cerebellar tonsil malformation, hydrocephalus, medulla and syringomyelia, secondary to osteomalacia, rickets, osteogenesis imperfecta and Clinical manifestations such as rheumatoid arthritis.

Symptoms of skull base depression Common symptoms Tinnitus visual impairment Increased intracranial pressure Dyspnea dysfunction Disorder sensation Disorder nausea upper extremity numbness after hairline hypoesthetic vertigo

Most patients have slow symptoms and occasional remission. Some patients can be asymptomatic. Only in the X-ray examination, there is a deformity of the occipital foramen magnum. The skull base is depressed. The patient may have a short neck, a low hairline, a crooked shape, and a cheek ear. Guo is asymmetrical, but has no obvious neurological symptoms.

Patients may have different symptoms and signs due to the degree of malformation and comorbidities. The general symptoms may include headache, dizziness, tinnitus, diplopia and vomiting. Patients may have head and neck deviation, asymmetrical cheeks, and thick neck. Short, posterior hairline, neck activity is limited and fixed at a special angular position, normal cervical anterior protrusion disappeared and abnormal appearance, patients often complain of neck stiffness, mostly with progressive lower limb weakness and walking difficulties as the first symptom, The onset is generally concealed, gradually worsening, or sudden onset or aggravation after head trauma, that is, slight numbness and weakness in the head after a slight trauma to the head or excessive head or neck, or even quadriplegia and difficulty breathing. Symptoms repeatedly and repeatedly, the whole condition is progressively worse.

The symptoms and signs of the nervous system are mainly characterized by the large occipital region syndrome. The main clinical manifestations are:

1. Upper cervical nerve root irritation symptoms: mainly due to skull base deformity bone stimulation and compression of the occipital fascia, ligament and dura mater, causing hyperplasia, hypertrophy or formation of fiber band, compression of the upper cervical nerve root, patient Often complained of chronic pain in the occiput, limited neck activity, decreased sensation, numbness on one or both upper limbs, pain, muscle atrophy, forced head position, etc.

2. The symptoms of the posterior group of cranial nerve disorders: often due to brain stem displacement, traction or arachnoid adhesions, the posterior group of cranial nerves involved, and dysphagia, cough, hoarseness, tongue muscle atrophy, speech is unclear, pharynx Symptoms of ball paralysis such as decreased reflexes, as well as symptoms such as decreased facial sensation, decreased hearing, and reduced corneal reflex.

3. Medulla and upper cervical spinal cord compression signs: mainly due to cerebellar tonsil sputum, local pathological tissue compression of the medulla and upper cervical spinal cord and secondary syringomyelia, patients with limb weakness, sensory disturbance, positive pyramidal tract sign , urinary retention, swallowing, difficulty breathing, fine finger movement disorder, positional dissipation; sometimes unilateral or bilateral segmental pain in the cervical and thoracic spine, temperature loss disappears, and tactile and deep feelings exist, this separation feeling The disorder is characterized by syringomyelia.

4. Cerebellar dysfunction: ocular nystagmus is common, mostly horizontal tremor, vertical or rotational tremor, cerebellar ataxia can occur in the late stage, manifested as unstable walking, unclear speech, visible body and nose test Not allowed, the knee test is not stable, and it is difficult to close the subject.

5. Vertebral artery blood supply disorders: manifested as paroxysmal vertigo, visual impairment, nausea and vomiting, ataxia, facial sensory disturbance, quadriplegia and ball paralysis.

6. Increased intracranial pressure symptoms: early patients generally do not have increased intracranial pressure, once it appears that the condition is serious, and mostly advanced, the symptoms are caused by obstructive hydrocephalus, and some patients with earlier occurrence may be combined with intracranial The cause of tumor or arachnoid cyst, the patient presented with severe headache, nausea and vomiting, optic disc edema, and even occipital foramen magnum, conscious disturbance, respiratory circulatory disturbance or sudden respiratory arrest and death.

Examination of skull base depression

Blood, urine, routine examination is normal, cerebrospinal fluid examination is generally no abnormalities.

Radiological examination of the cranial-neck positive lateral slice centered on the occipital macropore area, body slice, anterior and posterior open radiography (check sacral, pivotal), skull base radiography (check slope, odontoid), etc. The flat film of the brain, usually the cranial-cervical lateral slice can be diagnosed. It is the simplest method for diagnosing skull base depression. If necessary, CT scan and sagittal reconstruction can be used to observe the deformity of the large occipital region. In addition, according to the condition, myelography, cerebral angiography, ventriculography and cerebral angiography can be selected.

1. Skull flat film: The use of skull flat film to diagnose skull base depression requires various measurements. Because of the large local anatomical variation of the large occipital region, although there are many measurement methods, there is no ideal method for diagnosing this disease. It is very reliable, so at least two obvious abnormal measurements are needed to make a diagnosis based on the following methods.

(1) Chamberlain's line: also known as the sacral line, on the lateral side of the skull, from the trailing edge of the hard palate to the upper edge of the occipital foramen, which is the Qian line, the normal odontoid Below 3mm of this line, if it exceeds this limit, it is a skull base depression.

(2) Mc Gregor's line: also known as the basal line, from the trailing edge of the hard palate to the lowest point of the occipital scale, that is, the Mai's line, the normal odontoid should not be 6mm above the line, if it exceeds For the skull base depression.

(3) Bull angle: the angle formed by the plane of the hard palate and the plane of the atlas is normally less than 13°, and greater than 13° is the skull base depression.

(4) Base angle: the angle formed by the two lines from the base of the nose to the center of the sphenanus and the center of the saddle to the leading edge of the occipital foramen, normal from 109° to 148°, with an average of 132.3°. This angle increases when the skull base is depressed. .

(5) Klaus's index (Klaus's index): the vertical distance from the apex of the odontoid to the line between the saddle nodule and the occipital bulge, normal 40 ~ 41mm, if less than 30mm is the skull base depression.

(6) Second abdominal muscle groove connection (fishgold line): on the anterior and posterior segment of the skull, the line connecting the two abdominal muscle grooves, the distance from the dentate tip to the line, the normal is 5 ~ 15mm, if The apex of the odontoid is close to this line, even beyond this line, which is the depression of the skull base.

(7) Double mastoid line: the line between the two mastoids on the right side of the film. Normally, the line is passing through the occipital occipital joint. The dentate process can reach or exceed 1 to 2 mm above the line. In case of illness, this value is abnormal.

(8) Boogard angle: The angle formed by the anterior and posterior edge of the occipital foramen and the occipital slope is 119.5°~136°, and the angle is increased when the skull base is depressed.

(9) Outer ear hole height index: the distance from the midpoint of the skull, the center point of the outer ear hole or the midpoint of the outer ear hole to the forward extension of the anterior and posterior edge of the occipital foramen, which is the outer ear hole height index, normal 13 ~ 25mm, an average of 17.64mm, less than 13mm is the skull base depression.

2. CT scan: mainly shows changes in brain tissue and ventricle, sometimes cerebral ventriculography CT scan, CT scan after non-ionic water-soluble contrast agent in the ventricle, can observe the size of the ventricle, whether the midbrain tube is smooth and the first Changes in the ventricles and brainstem, and the location of the lower edge of the cerebellar tonsil.

3. MRI examination: MRI is one of the best methods for diagnosing this disease, especially in the sagittal position, which can clearly show the changes of the midbrain water tube, the fourth ventricle and brain stem, the degree of cerebellar tonsillar sac and the cervical spinal cord. The situation of pressure is convenient for determining the surgical treatment plan.

Diagnosis and identification of skull base depression

According to the age of onset, the course of the disease progresses slowly. The clinical manifestation is the syndrome of the occipital foramen and the characteristic appearance of the head. It can be diagnosed by X-ray examination. However, it is worth mentioning that the above various measurements are between men and women, children. There is a difference between them, so the measured value is not absolutely accurate. Therefore, when diagnosing this disease, comprehensive observation should be made on the presence or absence of bone changes and clinical signs in the large hole area of the occipital occipital bone. Comprehensive diagnosis is made for diagnosis, clinical application of CT scan and MRI There has been a breakthrough in the diagnosis of this disease, especially MRI is helpful for the early diagnosis of this disease, which shows clear cerebellar tonsil and syringomyelia in the lower jaw, which can not be done by conventional X-ray examination.

Differential diagnosis

1. Syringomyelia: syringomyelia often coexists with skull base depression. Its clinical features are isolated sensory disturbance in the cervical and thoracic spinal cord distribution area. The small muscles of the hand are often atrophied or even deformed, such as symptoms continue to increase, and If there is damage to the intracranial structure, the possibility of skull base depression should be considered. CT and MRI are helpful for diagnosis.

2. Upper cervical spinal cord tumor: This disease can be manifested as neck and occipital pain, diaphragmatic and intercostal muscle paralysis, hard limbs, progressive symptoms, early symptoms similar to skull base depression, but lack of skull base depression Features and features of intracranial structural involvement, X-ray or myelography contribute to differential diagnosis.

3. Primary lateral sclerosis: mainly manifested as bilateral pyramidal tract signs positive, that is, quadriplegia, such as lesions and cortical medullary bundles, dysphagia and hoarseness, but no sensory disturbance, cranial neck X-ray examination More normal.

4. Progressive spinal muscular atrophy: Because the lesion often begins from the lower cervical segment and the upper thoracic spinal cord anterior horn cells, the earliest manifestations are dual-finger weakness, unstable objects, small muscle atrophy of the hand and muscle fiber tremor, and gradually develop. To the forearm, arms and shoulders, there is generally no sensory disturbance, and the skull base X-ray examination is normal.

5. Cervical spondylosis: mainly manifested as upper limb muscle atrophy and long beam sign, often with radiculopathy, rare segmental sensory disturbance at the level of lesions, may have symptoms of vertebral artery insufficiency, but lack of cranial nerve involvement and cerebellum Symptoms, generally no increased intracranial pressure, cervical X-ray examination can be diagnosed.

6. Spinal cord syphilis: In the presence of proliferative cervical spinal dural meningitis, there may be upper limb sensory disturbances, atrophy and weakness and lower limb pyramidal tract signs, lack of manifestations of intracranial structural damage, myelography showing subarachnoid obstruction, Patients have a history of syphilis, a short history of spinal cord syndrome, positive blood and cerebrospinal fluid Fahrenheit and Kang's reaction, and can be clearly diagnosed by X-ray examination of the skull.

7. Others: The disease needs to be differentiated from posterior fossa tumor, cervical disc herniation and amyotrophic lateral sclerosis.

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