Ch. 2 - Neurosurgical investigation Flashcards
What is the flow of CSF circulation?
Choroid plexus (0.4 mL/min) -> lateral ventricles -> interventricular foramen -> 3rd ventricle -> aqueduct of Sylvius -> 4th ventricle -> foramen of Luschka/Magendie -> subarachnoid space -> arachnoid villi of dural sinuses (superior sagittal sinus)
Most common indications for LP
Infection, subarachnoid hemorrhage, MS, Guillan-Barre, neoplastic disease, myelography
Major contraindications for LP
- Clinical evidence of raised ICP
2. Local infection
At what vertebral level do you perform LP?
Approximately L3/L4, below conus
Common complications of LP
Worsening brain herniation/spinal cord compression, injury to neural structures, HA, backache, infection, implantation of epidermoid tumor
Best imaging modality to diagnose a spinal tumor
MRI
Most common complication of LP? How do you avoid it?
Spinal HA 2/2 low CSF pressure; avoid by:
- lying flat 12hrs post LP
- <20g needle, avoid multiple sticks
- blood patch
- hydration
Causes of xanthochromic (yellowish) spinal fluid
Hemorrhage, jaundice, hemolytic disease
Bacterial meningitis on LP?
PMNs, elevated protein, low glucose
Parasitic infection on LP?
Eosinophilia
Causes of elevated protein in CSF?
GBS, carcinomatosis, multiple myeloma, infection
Mononuclear pleocytosis in CSF?
Viral meningitis, TB meningitis, acute demyelination
Findings on CSF electrophoresis in multiple sclerosis
Stable oligoclonal band pattern over time
Causes of intracranial calcification
Meningiomas, craniopharyngioma, ependymoma, aneurysm, AVMs, and oligodendroglioma
Normal in pineal gland, choroid plexus, and falx
Cerebral abscess appearance on CT
Ring-enhancing lesion
What is bright on T1 MRI?
Fat is bright, CSF is black - good for detail of anatomic structures
What is bright on T2 MRI?
CSF is bright BUT on T2 FLAIR it is black
SPECT/PET
Measures cerebral blood flow or cerebral metabolism
What is an interference pattern in nerve conduction studies?
Voluntary muscle contraction producing motor unit potentials
What type of EMG interference pattern is seen with neuropathy?
Reduced interference 2/2 diminished motor units
What type of EMG interference pattern is seen with myopathy?
Normal interference pattern
