Glossary

Dorsal Root Entry Zone.  Refers to dorsal or posterior area of the spinal cord that is the entry site for sensory nerve rootlets.  This area is a surgical target for some pain and spasticity procedures (e.g., DREZ lesioning).

Drainage, irrigation, and fibrinolytic therapy – a therapy directed toward intraventricular hemorrhage with a goal of clearing hemorrhagic clot from the ventricle. The treatment consists of the placement of two externalized ventricular catheters with one in the frontal horn of one lateral ventricle and the other in the contra-lateral occipital horn. A solution of tPA, a fibrinolytic, is delivered by one catheter into the ventricles while the other catheter removes a volume of CSF so as to maintain an ICP below 7 mm Hg. Infusion stops when the CSF clears.

Digital subtraction angiography – A technique used to highlight circulatory vessels. Fluoroscopic radiographs are taken before and after the injection of a contrast media into the circulatory vessels. The image taken before the injection is then used to mask out or “subtract” bony or dense soft tissue seen on the images. This results in a highlighting of the vessels filled with contrast media.

Dural Sinus Malformation.  A congenital malformation of a dural venous sinus, typically found in the posterior fossa (Posterior sagittal sinus, transverse sinus or sigmoid sinus) and typically massive in size.

Congenital malformations of dural venous sinuses, typically found in the posterior fossa (Posterior sagittal sinus, transverse sinus or sigmoid sinus) and typically massive in size.

Diffusion Tensor Imaging – A MRI technique using a variant of diffusion weighted imaging to analyze white matter structure and integrity. Diffusion Tractography refers to a subsequent post-acquisitional processing that identifies white matter tracts.

Diffusion Tensor Imaging – A special type of diffusion weighted imaging (DWI) that is used to image white matter tracts (nerve axon tracts) within the central nervous system.  White matter tracts’ axons have physical properties that are anisotropic (directionally dependent) and this causes variation in the rate of water molecule migration in a magnetic field depending on direction.  DTI measures this variability to generate images or maps of white fiber tract orientation within the CNS.

Deep Tendon Reflex(s): Also referred to as ‘muscle stretch reflex.  An examination of the sensitivity of muscles to a sensory input.  The tendon of a muscle is tapped by an examination hammer (tendon stretched), the muscle senses the stretch and sends a signal to the spinal cord, the spinal cord reacts to this signal (afferent sensory signal or nerve potential) and causes a signal (efferent motor signal or nerve potential) to be sent back to the muscle causing it to contract (hence causing movement such as a leg jerking in response to tapping the knee tendon).

A technique for increasing imaging contrast between dissimilar tissues.  Biological tissues attenuate X ray beams to differing extents depending on (a) the nature of the tissue and (b) the energy of the X ray beam. First generation CAT scanners used X ray at a single energy level. By using two X ray sources, at differing energy levels (dual energy technique), contrast definition between tissues and therefore image resolution can be improved.

A condition where abnormal cranial nerve development results in a limited ability to move the eyes outward. There is also abnormalities in the bones of the hands or absent thumbs, extra thumbs and absent of the bones of the forearm to a varying degree.