HY lecture notes:
Slightly move quantitative version of the above chart (but qualitative suffices for the USMLEs):
Herpes causes temporal lobe hemorrhage, which is why there’s blood in the CSF. CT can often be negative, but one thing I have seen in Qs is “slowing pattern” or “temporal complexes” on EEG, essentially implying HSV encephalitis.
Meningitis = nuchal rigidity (stiff neck), headache, and photophobia. Can also present with ophthalmoplegia.
Encephalitis (encephalopathy more generically) = confusion.
Meningoencephalitis = combination of the two.
Chiari malformation = downward displacement of the cerebellar tonsils through the foramen magnum. There are many types.
Type I is less severe than type II. Type II is aka Arnold-Chiari malformation.
Type I presents with syringomyelia of the cervical spinal cord, which is a syrinx (fluid filled cyst within the spinal cord) affecting the anterior white commissure –> causes bilateral loss of pain and temperature sensation below the level of the lesion. Type I vignettes will generally be in a young adult.
Type II presents with a more severe inferior displacement of the tonsills + vermis than type I. It is accompanied by a lumbar or lumbosacral myelomeningocele. Only type II is referred to as the Arnold-Chiari malformation.
Immunodeficiency + autoimmune disease increase risk for non-Hodgkin lymphoma, namely primary CNS lymphoma. If they show you a large-ish, irregular primary lesion with tiny adjacent lesions, the latter are merely satellite lesions. I point this out because metastases are classically multiple lesions, but the pattern is not that of a large lesion with adjacent tiny satellite lesions. USMLE likes SLE causing CNS lymphoma (they will show you an irregular ring-enhancing lesion + tell you explicitly that it’s a ring enhancing lesion + patient has SLE –> answer = CNS lymphoma, not Toxo).
