Neuroradiology Pearls

Dr. Montanera

April 8, 2005

 

CT first invented in 1973 by Hounsfield.

Helped us go from 2D to 3D images.

 

CT quick, reliable, low cost, good for calcium.

 

MR actually was invented in the 1940s, but computing power inadequate.

 

MRI involves hydrogen nuclei magnetic moment begin aligned in a magnet, then a radiofrequency pulse causing precession.

 

MRI provides better resolution and ability to discriminate soft tissues, e.g. brain tumours.

T1 and T2 are properties of the tissues. MRI also removes bone artifacts in the posterior fossa that you get in CT. Also you have a multiplanar capability. But weakness in detection of calcification. Also more claustrophobic. But no radiation.

Principle of cellular density (nucleus/cytoplasmic ratio) to help determine diagnosis. And contrast enhancement helps as a blood-brain barrier marker.

 

T1

            proteinaceous fluid

-         methemoglobin

-         fat

-         melanin

-         calcium, manganese, copper

 

Tumors:

- extraaxial VS. intraaxial

  1. look for CSF cleft
  2. blood vessels
  3. effect on underlying brain

- DWI

            - Water diffusion

            - bright if restricted diffusion

- MR spectroscopy

- NAA nonspecific but detects neuronal loss.

- Perfusion imaging

 

Mets

-         multiple

-         intraaxial

-         lots of edema

-         grey-white interface

 

CSF dissemination

 

Anatomical clues

            -e.g. cyst, intraaxial, blood vessels – hemangioblastoma most common adult primary posterior fossa tumour

 

Common sella tumours

-Pituitary adenoma

-Rathke’s cleft cyst

-trigeminal schwannoma

 

Skull base tumours

-         chordoma

-         chondrosarcoma

-         esthsioneuroblastoma

-         lymphoma

-         met

-         myeloma

-         paraganglioma

-         sinonasal carcinoma

 

Pineal

-         pineal, germ cell origin tumours

-         meningioma

 

CP angle

-         schwannoma

-         meningioma

-         epidermoid

-         arachnoid cyst

-         paraganglioma

 

Intravent

-         ependymoma

-         subependymoma

-         choroids plexus papilloma

-         cenral neurocytoma

-         colloidcyst

-         meningioma

-         giant cell astrocytoma

 

Mimics

-         abscess

-         thrombosed aneurysm

-         mesial temporal sclerosis

-         HSV encephalitis

-         Dural AV fistula

 

CNS calcifications

-         physiology

-         infection

-         neoplastic

-         trauma

-         vascular, aneurysm

-         endocrine

-         toxic/metabolic, e.g., Fahrer’s disease

-         developmental

-         misc

 

Bleeds

-         epidural – biconvex

-         subdural – cresenteric,  isodense if chronic

-         subarachnoid

-         on FLAIR, you see loss of black CSF spaces

 

Nontraumatic bleeds

-         hypertensive hemorrhages

-         vascular – aneurysm, AVM, cavernous malformation

-         infarcts

-         coagulopathy

-         neoplasm

-         drug related – cocaine, phenylephedrine, anticoagulants, fibrinolytics

-         vasculitis, vasculopathy – amyloid angiopathy

-         infection – encephalitis, herpes, fungal

-         germinal matrix hemorrhage

 

George Washington Bridge Oreo Cookie

T1 - Grey White Black

T2 – Black White Black

 

If MRI done early, can’t rely on methemoglobin on MRI imaging for detecting thrombosis.