Arteriovenous malformations of the brain are congenital anomalies of the blood vessels that are derived from maldevelopment of the capillary network, allowing direct connections between cerebral arteries and veins. The most common presenting symptoms are cerebral hemorrhage and seizures. Focal neurologic deficits and headaches may develop independent of cerebral bleeding. As a result of the widespread use of brain imaging, arteriovenous malformations are increasingly being discovered incidentally.
Stereotactic radiosurgery is an appropriate form of therapy for patients who have one to four brain metastases, no larger than 4 cm in diameter, from metastatic cancer. It appears to be effective for all types of primary tumors, even those that have been considered to be resistant to conventional radiation therapy.
Clinical Criteria for Brain Death in Adults and Children
- Absence of motor responses
- Absence of pupillary responses to light and pupils at midposition with respect to dilatation (4–6 mm)
- Absence of corneal reflexes
- Absence of caloric responses
- Absence of gag reflex
- Absence of coughing in response to tracheal suctioning
- Absence of sucking and rooting reflexes
- Absence of respiratory drive at a PaCO2 that is 60 mm Hg or 20 mm Hg above normal base-line values*
- Interval between two evaluations, according to patient’s age Continue reading
Acute: Subtle low signal (hypointense) on T1, often difficult to see at this stage, and high signal (hyperintense) on spin density and/or T2-weighted and proton density-weighted images starting 8 h after onset; should follow vascular distribution. Mass effect maximal at 24 h, sometimes starting 2 h after onset, even in the absence of parenchymal signal changes. No parenchymal enhancement with paramagnetic contrast agent. Territorial intravascular paramagnetic contrast enhancement of “slow-flow” arteries in hyperacute infarcts; at 48 h, parenchymal and meningeal enhancement can be expected.
Infarction: focal hypodense area, in cortical, subcortical, or deep gray or white matter, following vascular territory, or watershed distribution. Early subtle findings include obscuration of gray/white matter contrast and effacement of sulci, or “insular ribbon.”
The imaging characteristics of blood on MRI can be variable: