• Achondroplastic – A hereditary condition in which the growth of long bones by ossification of cartilage is retarded, resulting in very short limbs and sometimes a face that is small in relation to the (normal-sized) skull.
  • Acute – Sharp, severe, having sudden onset, sharp rise and short course; lasting a short time; seriously demanding urgent attention.
  • Acute Care – The phase of managing health problems which is conducted in a hospital on patients needing medical attention.
  • Adiadochokinesia – Inability to stop one movement and follow it immediately with movement in the opposite direction.
  • Afferent Neuron – a neuron conducting impulses inwards to the brain or spinal cord.
  • Agnosia – Failure to recognize familiar objects although sensory mechanism is intact. May occur for any sensory modality.
  • Agraphia – Inability to express thoughts in writing.
  • Akinetic Mutism – A condition of silent, alert-appearing, immobility that characterizes certain subacute or chronic states of altered consciousness. Sleep-wake cycles have been retained, but no observable evidence for mental activity is evident; spontaneous motor activity is lacking; person appears to be aware but inactive. Exhibited by persons with high brain stem lesions.
  • Alexia – Inability to read.
  • Allograft – A tissue graft from a donor genetically unrelated to the recipient.
  • Amyotrophic Lateral Sclerosis – (ALS, motor neuron disease, Lou Gehrigs disease). A degenerative disorder affecting the motor neuron cells and the motor tracts in the brain and spinal cord.
  • Analgesia – The absence of pain.
  • Anasthesia – Loss of bodily sensation with or without loss of consciousness.
  • Anasthesia, Block – Anesthesia of an area supplied by a nerve; produced by an anesthetic agent applied to the nerve.
  • Anasthesia, Local – Loss of sensation in a small area of the body.
  • Aneurysm – A balloon-like deformity in the wall of a blood vessel. The wall weakens as the balloon grows larger, and may eventually burst, causing a hemorrhage.
  • Angiogram – An invasive diagnostic test that uses a special dye injected into the arteries by a catheter to visualize the blood vessels.
  • Anterior Cervical Discectomy and Fusion (ACDF) – a common surgical procedure to treat nerve root or spinal cord compression by decompressing the spinal cord and nerve roots of the cervical spine in order to stabilize the corresponding vertebrae.
  • Anticoagulant – A substance that prevents coagulation; that is, it stops blood from clotting.
  • Aphasia – Loss of the ability to express oneself and/or to understand language. Caused by damage to brain cells rather than deficits in speech or hearing organs.
  • Aphemia – The isolated loss of the ability to articulate words without loss of the ability to write or comprehend spoken language.
  • Apraxia – Inability to carry out a complex or skilled movement; not due to paralysis, sensory changes, or deficiencies in understanding.
  • Arachnoid Mater – A layer of the meninges, membranes that contain the central nervous system.
  • Arteries – The blood vessels that carry the oxygenated blood to the organs.
  • Arteriovenous Malformation (AVM) – A “tangle” of blood vessels present from birth which may be prone to bleeding.
  • Atherosclerosis – Thickening of the arterial wall of blood vessels due to deposition of lipids (fats) and blood clots.
  • Arthrodesis (also known as Artificial Ankylosis or Syndesis) – The artificial induction of joint ossification between two bones via surgery. This is done to relieve intractable pain in a joint which cannot be managed by pain medication, splints, or other normally-indicated treatments.
  • Arthralgia – Joint pain.
  • Arthritis – A group of conditions involving damage to the joints of the body.
  • Arthroplasty – Surgical reconstruction or replacement of a malformed or degenerated joint.
  • Aspiration – When fluid or food enters the lungs through the wind pipe. Can cause a lung infection or pneumonia.
  • Ataxia – A problem of muscle coordination not due to apraxia, weakness, rigidity, spasticity or sensory loss. Caused by lesion of the cerebellum or basal ganglia. Can interfere with a person’s ability to walk, talk, eat, and to perform other self care tasks.
  • Atrial Fibrillation – An abnormal rhythm of the heart that can result in an increased risk of stroke due to the formation of emboli (blood clots) in the heart.
  • Atrophy – A wasting away or decrease in size of a cell, tissue, organ, or part of the body caused by lack of nourishment, inactivity or loss of nerve supply.
  • Avascular – Without blood vessels.
  • Autoimmune – An abnormal response of the immune system, causing antibodies and immune mediated cells to attack parts of the body. This mechanism may explain many diseases.
  • Axis – The second cervical vertebra on which the head turns.
  • Axon – The inner core of peripheral nerves.
  • American Association of Neurological Surgeons
  • American Board of Neurological Surgery
  • American Medical Association
  • The Congress of Neurological Surgeons
  • College of Physicians and Surgeons of Newfoundland & Labrador
  • North American Skull Base Society
  • North American Spine Society