Craniovertebral anomalies are deviations in the anatomical interposition and structure of the structures of the area of contact of the skull and spine. Often they do not have clinical manifestations. In clinically significant cases, symptoms of intracranial hypertension, lesions of the vertebral artery, compression of the spine, spinal cord or trunk manifest; respiratory disorders are possible in young children. Craniovertebral anomalies are diagnosed using craniography, MRI or CT of the craniovertebral region. It is necessary to observe a neurologist, according to indications — neurosurgical treatment.
ICD 10
Q67 Q76.1 Q76.5
General information
The craniovertebral junction includes the base of the skull formed by the occipital bone and the first 2 cervical vertebrae (Atlas and axis). This is the junction area of the stationary cranium and the mobile spine. Violations of the correct anatomical structure and position of bone formations underlying craniovertebral anomalies (CVA) are often reflected in the structures of the brain and spinal cord located in this area, which leads to the appearance of appropriate neurological symptoms. The latter is quite variable in nature, mainly associated with compression of the upper neck segments of the spinal cord and spinal roots, brain stem, cerebellum, IX-XII cranial nerves, vertebral arteries; impaired circulation of cerebrospinal fluid. Mild craniovertebral abnormalities occur subclinically, but their detection is important in clinical neurology, especially when it comes to manual therapy.
Causes
Congenital anomalies of the craniovertebral junction occur as a result of impaired embryogenesis when exposed to variable negative factors on the fetus. The latter include increased radioactive background, intrauterine infections, intoxication with dysmetabolic diseases, occupational hazards or addictions (drug addiction, smoking, alcoholism) of a pregnant woman. In a number of families, there is a significantly higher frequency of anomalies than in the general population, which speaks in favor of hereditary transmission of CVA, which is probably multifactorial.
Acquired craniovertebral anomalies can be formed as a result of spinal injuries in the cervical region or traumatic brain injuries, including birth injuries of a newborn. In addition, injuries often serve as a trigger that provokes clinical manifestations of a previously asymptomatic anomaly. Deformations of the craniovertebral zone are possible due to osteoporosis, which can be caused by rickets, hyperparathyroidism, deforming osteitis, osteomalacia. Acquired craniovertebral anomalies may occur due to the destruction of bone structures of the craniovertebral junction in osteomyelitis, bone tumors, tuberculosis, actinomycosis, syphilis.
Symptoms
The clinical picture of anomalies of the craniovertebral junction is very variable: from a subclinical course to the occurrence of gross neurological disorders. It is caused by the type and degree of existing bone defects. Visual signs characterizing craniovertebral anomalies include: low hair growth on the back of the head, shortened neck, limited head mobility, enlarged cervical lordosis, torticollis, altered head position. The manifestation of the clinic depends on the severity of the anomaly. With severe deformity, it usually occurs in early childhood, with moderate and mild — it is possible at any age period, but it is usually delayed.
Clinical symptoms can be represented by vertebral artery syndrome and chronic cerebral ischemia, syncope, hydrocephalus and intracranial hypertension, in severe cases — the syndrome of insertion of the trunk and tonsils of the cerebellum into the occipital foramen. In young children, craniovertebral abnormalities can be the cause of sleep apnea syndrome, stridor, etc. respiratory disorders.
Types
The pro-atlantean is a rudimentary bone element in the occipital bone. Congenital pathology associated with a violation of the reduction of the connective tissue cord formed from the ventral side of the vertebrae during ontogenesis. In the absence of accretions of the rudimentary element with the surrounding bone structures, they speak of a free pro-atlantean. When it merges with the anterior edge of the large occipital foramen, the term “third condyle” is used, when fusing with the posterior edge, the term “occipital process” is used.
Hypoplasia and aplasia of the posterior arch of the atlas. In the first case, there are no clinical manifestations, the defect is diagnosed radiologically. The anomaly occurs in 5-9% of the population. In the second case, compression of the distal part of the trunk and the upper parts of the spinal cord occurs in childhood or puberty. Characterized by a rapid aggravation of symptoms. The occurrence of the defect is 0.5-1%.
Assimilation of the Atlas is the fusion of the 1st cervical vertebra and the occipital bone. It can be complete and incomplete, one- and two-sided. The frequency of the anomaly does not exceed 2%. Atlanta assimilation manifests clinically after the age of 20 with headaches with vegetative symptoms. Possible cerebrospinal hypertension syndrome, mild dissociated sensory disorders, disorders of the function of the lower cranial nerves.
Anomalies of the dentoid process, according to various data, occur in 0.5-9% of the population. They include hypo- and aplasia, as well as hypertrophy of the process, which occur without clinical manifestations. Neurological symptoms occur in cases when the dentoid process is not fused with the axis, but forms a separate dentoid bone. In such conditions, there is a chronic atlanto-axial subluxation, possible compression of the proximal parts of the spinal cord.
Platybasia — flattening of the base of the skull. Clinically, platybasia manifests itself only with the III degree of flattening, accompanied by a significant decrease in the size of the posterior cranial fossa, entailing intracranial hypertension, compression of the cerebellum and IX-XII pairs of cranial nerves.
Basilar impression is the indentation of the base of the skull into its cavity. In the population it occurs with a frequency of 1-2%. With basilar impression, symptoms caused by a decrease in the posterior cranial fossa are combined with signs of compression of the spinal roots of the first cervical segments. Compression myelopathy with central tetraparesis may occur in these segments. The extreme severity of the anomaly (screwing the base into the skull cavity) is called convexobasia.
Kimmerli anomaly is associated with the presence of an additional Atlas arch, which restricts the vertebral artery. Kimmerli anomaly can be complete and incomplete, one- and two-sided. Clinically significant only in a quarter of carriers of the defect. It is manifested by vertebral artery syndrome, syncope, TIA, in severe cases, ischemic stroke is likely.
Chiari anomaly is a congenital malformation in which part of the structures of the posterior cranial fossa prolapses into the occipital foramen. 80% of patients have syringomyelia. There are 4 types of Chiari anomaly, which differ in the age of debut and clinical symptoms.
Klippel-Feil syndrome is a rare congenital anomaly (frequency 0.2—0.8%) in the form of a decrease in the number of cervical vertebrae and/or their fusion. It may be hereditary or sporadic. Klippel-Feil syndrome is often combined with other malformations (spina bifida, polydactyly, cleft palate, dental anomalies, congenital heart defects, etc.). Muscle weakness that occurs in early childhood with an outcome in paresis is characteristic. In some cases, congenital hydrocephalus and oligophrenia are observed.
Diagnostics
Along with the clinical examination, it is important in the diagnosis to perform radiography of the skull and radiography of the cervical spine. In order to visualize the soft tissue structures of the craniovertebral junction, an MRI of the brain and an MRI of the spine in the cervical region are prescribed. The study is performed in T1 and T2 modes, in sagital and axial projections. According to the indications, an MRI of the cerebral vessels is performed. If an MRI examination is impossible, as well as for more accurate visualization of bone formations of the craniovertebral zone, CT of the spine and CT of the brain are performed.
Additionally, an ophthalmologist is consulted with ophthalmoscopy (examination of the fundus), an otoneurologist is consulted with audiometry, indirect otolithometry. If necessary, stem evoked potentials are examined. The presence of vertebral artery syndrome is an indication for vascular studies — REG with functional tests, ultrasound of extracranial vessels. To identify hereditary pathology, a geneticist and genealogical analysis are consulted.
Treatment
Patients with craniovertebral junction anomalies should observe a number of precautions so as not to provoke or aggravate the clinical manifestations of the anomaly. Sharp tilts and turns of the head, headstands, somersaults, traumatic sports and forced loads are not desirable. Observation of subclinical forms of CVA and basic therapy for moderate manifestations is carried out by a neurologist. Traditionally, the basis of basic treatment consists of nootropic, neurotrophic and vasoactive pharmaceuticals, although their effectiveness in craniovertebral anomalies has not been proven.
With pronounced clinical manifestations, the question of the possibility of neurosurgical correction of the defect is solved. Indications for surgical treatment are symptoms of compression of the trunk, cerebellum or spinal cord, violation of cerebral circulation. With basilar impression and Chiari anomaly, craniovertebral decompression is performed, with Kimmerli anomaly — resection of the additional atlas arch, with Atlanta assimilation — laminectomy for decompression of the spinal cord and stabilization of the spine with spinal fusion, with Klippel-Feil syndrome — cervicalization operation.