Glossary

Neural tube defect. A failure in closure of the neural tube during the first trimester of fetal development. It is one of the most common types of developmental anomalies, occurring in 1 of every 1000 births. Myelomeningoceles and anencephaly are common examples.

retraction nystagmus or convergence-retraction nystagmus- On fast up-gaze, the eyes pull in and the globes retract. This is generally a sign of central nervous system dysfunction, typically involving the midbrain.

O6-methylguanine – this is a naturally occuring protein (alkylated guanine) that induces DNA mutations and it is removed by MGMT. It is felt to be carcinogenic.

Having few symptoms.  A paucity of symptoms.

Oncosphere: The larval form of a tapeworm that has been ingested by an intermediate host animal.

Overall survival.  This term is used to define the time until death after a treatment.

Posterior Atlanto-Dental Interval.  This is the horizontal distance from the posterior (dorsal) odontoid surface to the anterior (ventral) surface of the posterior arch of the atlas. This measures the  space available for the spinal cord (so-called SAC).  A value of less than 13 mm suggests cord compression.

– aka dorsal midbrain syndrome: Abnormalities in eye movement and pupillary function die to a lesion in the midbrain. The abnormal eye movements associated with this syndrome are paralysis in upgaze, paresis in accommodation with convergence-retraction nystagmus and sunsetting due to retraction of the upper eyelids (sun setting).

pB-C2 line – Also referred to as the Grabb-Oakes line. A line drawn through the odontoid that is perpendicular to a line extending from the posterior basion to posterior-inferior body of C2. The distance of the segment of this line from the anterior edge of the odontoid to the ventral dura represents the degree of encroachment of the odontoid into the upper spinal canal and potential ventral brainstem compression.

Patient controlled analgesia – refers to any method that allows a patient to control their administration of pain medication. Typically the delivery mechanism is set up so that an over-dosage of medication cannot be delivered.