Glossary

Gradient Recalled Echo or “gradient” MRI.

Gross total resection. this refers to the resection of a tumor to a point where none is visible to the naked eye on inspection of the surgical cavity. With the introduction of magnified vision in the operating room many use the term to refer to resection to a point where no tumor is visible when the surgical bed is viewed through a surgical microscope.

Gross tumor volume – a term used when discussing radiotherapy that describes the tumor bed at risk for recurrence or progression. Usually defined by MRI or CT scan.

Gray unit-the SI unit of absorbed radiation dose of ionizing radiation (for example, X-rays). This replaces the traditional rad (equivalent to 0.01 Gy).

Hoffman Reflex. 1A sensory fiber stimulated evoking a muscle contraction recorded by EMG. Analogous to a stretch reflex.

Hoffman Reflex. 1A sensory fiber stimulated evoking a muscle contraction recorded by EMG. Analogous to a stretch reflex.

A line drawn from the midline, dorsal surface of the anterior Foramen Magnum to the ventral (anterior) tip of the dens.  If the length of this lines exceeds 12 mm then an occipitalcervical dissociation is suggested.

Hemoglobin S/Beta Zero Thalassemia.  A condition similar to Sickle Cell Disease where one abnormal hemoglobin S gene and one abnormal hemoglobin beta thalassemia gene are inherited resulting in the disease.  This condition is less severe than Sickle Cell Disease.

Hemoglobin SS Disease or Sickle Cell Disease. A genetic blood disorder where two copies of the abnormal hemoglobin S gene are inherited, resulting in the production of abnormal hemoglobin molecules that can form rigid, sickle-shaped red blood cells.

Human chorionic gonadotrophin – a hormone normally produced by the placenta in a pregnant woman. It is also produced by embryonal tumors and a finding of elevated blood or CSF levels of this tumor may be indicative of the existence of such a tumor.