Glossary

Ommaya reservoir
a small plastic reservoir that can be implanted under the scalp and is then connected to one of the brain’s ventricles; the shape of the Ommaya reservoir is reminiscent of a small pillow. At its bottom, it is connected by a tube (ventricular catheter) to one of the cerebral chambers (usually the right lateral ventricle) or another cavity in the brain filled with cerebrospinal fluid (CSF) (e.g. arachnoid cyst). The Ommaya reservoir (or Rickhams reservoir, another model with a similar mechanism) is implanted as part of a short, neurosurgical procedure. Such a reservoir can be connected to a shunt system for the long-term treatment of hydrocephalus or to a ventricular catheter.
Example / Relevance Pediatrics: (ventricular) accesses such as the Ommaya reservoir are required as part of the treatment of some brain tumour, e.g. to remove cerebrospinal fluid (CSF) for diagnostic or therapeutic purposes (so-called ventricular puncture) or for the controlled administration of drugs (such as cytostatics, antibiotics) into the cerebrospinal fluid. Ventricular access may also be used in the diagnosis and treatment of leukaemia and Non-Hodgkin lymphoma.

operability
feasibility of surgery as a treatment option; whether a patient is operated depends on their clinical condition and on whether the procedure is an appropriate and effective form of treatment in the respective case (indication). The operability of a tumour particularly depends on its location in the body and its growth behaviour.

ophthalmological
referring to the eye or eye care (ophthalmology)

opsoclonus-myoclonus-ataxia syndrome (Abrev.: OMAS) syn. "dancing eye syndrome", Kinsbourne syndrome
manifests itself as a combination of short, fast and irregular eye movements in different directions, involuntary jerky muscle twitches of the arms and legs, and a disturbance in movement coordination; In 70-80% of those affected, OMAS is associated with chronic neurological and intellectual deficits, cognitive and motor developmental delays, language deficits and behavioural problems.
Example / Relevance Pediatrics: OMAS occurs in 1–4% of patients with newly diagnosed neuroblastomas.

optic nerve syn. Nervus opticus, second cranial nerve
first section of the visual pathway that starts from the retina in the eye and leads to the visual center of the cerebral cortex; the optic nerve consists of the processes (axons) of the nerve cells of the retina and thus contains a total of about one million nerve fibers. The optic nerve, which has an average length of 4.5 cm, can be divided into three parts: one in the eyeball, one in the eye socket (orbit) and one part in the skull.
Example / Relevance Pediatrics: the optic nerve exits the eyeball at the so-called optic nerve papilla, which can be viewed directly with the ophthalmoscope as part of an eye examination (fundoscopy). A swelling and button-shaped protrusion of the optic nerve papilla towards the examiners eye is indicative of increased intracranial pressure, e.g. caused by a brain tumour. For this reason, if a brain tumour is suspected, a fundoscopy of the eye is always performed for initial diagnostics.

oral
belonging to the mouth, through the mouth, from the mouth

osteosarcoma
the most common bone tumour in childhood and adolescence; occurs mainly in the second decade of life during the pubertal growth phase
Main Information Document: Osteosarcoma

outpatient
non-inpatient medical care: the patient does not stay overnight in the medical facility for diagnostic and/or treatment center, but can go home the same day.