Basilar invagination occurs when the top of the C2 vertebrae migrates upward. It can cause the opening in the skull where the spinal cord passes through to the brain (the foramen magnum) to narrow. It also may press on the lower brainstem.

This is similar to Chiari malformation. That, however, is usually present at birth.

Symptoms

Symptoms vary depending on whether the spinal cord, brain stem, nerves or their blood supply is affected by the pressure.

Symptoms become apparent when the neck is bent. They include:

• Posterior head pain
• Neck weakness
• Periods of confusion
• Dysarthria
  Dysarthria
  Dysarthria is a motor speech disorder resulting from neurological injury of the motor component of the motor-speech system and is characterized by poor articulation of phonemes...
  
   (difficulty swallowing or talking due to loss of muscle control)
• Dizziness
• Loss of sensation
• Cranial nerve disturbance
• Loss of the ability to know how joints are positioned
• Lhermitte's sign
  Lhermitte's sign
  Lhermitte's sign, sometimes called the Barber Chair phenomenon, is an electrical sensation that runs down the back and into the limbs. In many patients, it is elicited by bending the head forward...
  
   (tingling when the neck bends backward)
• Weakness of the arms and legs
• Orthostatic hypotension
  Orthostatic hypotension
  Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when the person stands up or stretches. The decrease is typically greater than 20/10 mm Hg, and may be...
  
  
• Patients will go into a pool and notice that below their belly button the water is not as cold as it is above.

Complications from this can include hydrocephalus

Hydrocephalus

Hydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...

, pseudotumor cerebri or syringomyelia

Syringomyelia

Syringomyelia is a generic term referring to a disorder in which a cyst or cavity forms within the spinal cord. This cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord. The damage may result in pain, paralysis, weakness, and stiffness in the back, shoulders, and...

 because it blocks the flow of fluid around the brain and spinal cord.

Causes and Risk Factors

Basilar invagination can be present at birth. If the condition develops after birth, it is usually the result of injury or diseases. If due to injury, about half the time it is caused by vehicle or bicycle accidents; 25% of the time by falls and 10% of the time by recreational activities such as diving accidents.

It also occurs in patients with bone diseases, such as osteomalacia

Osteomalacia

Osteomalacia is the softening of the bones caused by defective bone mineralization secondary to inadequate amounts of available phosphorus and calcium, or because of overactive resorption of calcium from the bone as a result of hyperparathyroidism...

, rheumatoid arthritis

Rheumatoid arthritis

Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...

, Paget's disease

Paget's disease

Sir James Paget, a surgeon and pathologist, described several diseases, including:* Paget's disease of bone * Paget's disease of the breast* Paget-Schroetter disease* Extramammary Paget's disease...

, Ehlers-Danlos syndrome

Ehlers-Danlos syndrome

Ehlers–Danlos syndrome is a group of inherited connective tissue disorders, caused by a defect in the synthesis of collagen . The collagen in connective tissue helps tissues to resist deformation...

, Marfan syndrome

Marfan syndrome

Marfan syndrome is a genetic disorder of the connective tissue. People with Marfan's tend to be unusually tall, with long limbs and long, thin fingers....

, and osteogenesis imperfecta

Osteogenesis imperfecta

Osteogenesis imperfecta is a genetic bone disorder. People with OI are born with defective connective tissue, or without the ability to make it, usually because of a deficiency of Type-I collagen...

.

Diagnosis

A doctor will base his or her diagnosis on the symptoms the patient has and the results of tests, including:

• An X-ray
  X-ray
  X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
  
  
• Magnetic resonance imaging
  Magnetic resonance imaging
  Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
  
   (MRI), which usually provides the most information
• Computed tomography
  Computed tomography
  X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
  
   (CT) scan

Treatment

If there aren't neurological symptoms (such as difficulties moving, loss of sensation, confusion, etc.) and there is no evidence of pressure on the spinal cord, a conservative approach may be taken such as:

• Drugs, such as aspirin
  Aspirin
  Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
  
  , without steroids to relieve inflammation
• Cervical traction, in which the neck is pulled along its length, thus relieving pressure on the spinal cord
• Using a neck collar or cervical-thoracic suit

If there is pressure on the spinal cord or life-threatening symptoms are present, surgery is recommended.

See also

• Chiari Malformation
• Syringomyelia
  Syringomyelia
  Syringomyelia is a generic term referring to a disorder in which a cyst or cavity forms within the spinal cord. This cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord. The damage may result in pain, paralysis, weakness, and stiffness in the back, shoulders, and...
  
  
• Hydrocephalus
  Hydrocephalus
  Hydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...
  
  
• Rheumatoid arthritis
  Rheumatoid arthritis
  Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...
  
  
• Ehlers-Danlos Syndrome
  Ehlers-Danlos syndrome
  Ehlers–Danlos syndrome is a group of inherited connective tissue disorders, caused by a defect in the synthesis of collagen . The collagen in connective tissue helps tissues to resist deformation...
  
  
• Marfan Syndrome
  Marfan syndrome
  Marfan syndrome is a genetic disorder of the connective tissue. People with Marfan's tend to be unusually tall, with long limbs and long, thin fingers....
  
  
• Dysautonomia
  Dysautonomia
  Dysautonomia is a broad term that describes any disease or malfunction of the autonomic nervous system. This includes postural orthostatic tachycardia syndrome , inappropriate sinus tachycardia , vasovagal syncope, mitral valve prolapse dysautonomia, pure autonomic failure, neurocardiogenic...