Diastematomyelia

occurs in 5% of patients with scoliosis

is associated with a myelomeningocoele in more than half the patients

is associated with a cutaneous naevus in more than half the patients

affects men and women equally

is associated with a double thecal sac in 75% of cases

Brainstem gliomas

commonly calcify

commonly form cysts

rarely bleed

are best demonstrated on CT

enhance strongly on CT with contrast

Regarding cerebral infarction

most infarcts enhance with contrast at some stage, on CT, usually before 24 hours

petechial haemorrhage is well demonstrated on MRI

90% are visible on CT by 48 hrs

in the anterior cerebral artery territory it is most often due to arterial spasm after sub-arachnoid haemorrhage

"lacunar" infarcts are well seen in the early stages

Haemorrhagic brain metastases occur with the following primary sites

gastrointestinal tract

bronchus

renal cell carcinoma

breast

ovary

Early venous filling on cerebral angiography is seen in

lymphoma

metastases

meningioma

craniopharyngioma

chordoma

Meningiomas

form 25% of primary intracranial tumours

calcification is seen on plain films in 50%

hyperostosis is seen in 90% of basal tumours

may enlarge the internal auditory meati

are homogenous on MRI

Acoustic neuromas

most commonly affect the cochlear division of the eighth cranial nerve

are hyperdense compared to brain and enhance with contrast on CT

are best demonstrated by MRI

when bilateral are pathognomic of Von Recklinghausen's disease

may cause expansion of the internal auditory meatus

Chordomas

occur in the sacral region in one third of cases

are homogeneous on MRI

are hypodense compared to brain on CT

usually occur in the midline

can resemble chondrosarcomas

Cerebral abscesses

are most commonly caused by streptococci

25% arise from haematogenous spread of infection

25% arise from spread of infection from adjacent structures

often contain gas

tend to be loculated

Intracranial aneurysms

are "giant" if larger than 10 mm

10% arise from the anterior communicating artery

containing thrombus have low T2 signal on MRI

calcification is uncommon

are multiple in 20% of cases