CT before lumbar puncture

LP without CT is likely safe if:

1. History
   1. Age < 60
   2. Not immunocompromised
   3. No history of CNS disease
   4. No seizure within 1 week of presentation
2. Physical Exam
   1. No ALOC
   2. No inability to answer two consecutive questions successfully
   3. No inability to follow two consecutive commands successfully
   4. No gaze palsy
   5. No abnormal visual fields
   6. No facial palsy
   7. No arm drift
   8. No leg drift
   9. No abnormal language

If none of the above, chance of normal ct is 97%; none of the patients herniated

CT findings that prohibit LP

1. Midline shift
   1. Look for unequal pressures between the 3 cerebral compartments (left/right supretentorial compartments, posterior fossa)
   2. Look for intracerebral masses not causing midline shift
2. Obsutrictive hydrocephalus
   1. Look for enlargement of ventricles prox to lesions and normal ventricles distal (especially 4th ventricle)
3. Basilar cisterns compressed
   1. Lateral/3rd ventricles may be small due to diffuse cerebral edema or enlarged due to obstr. hydroceph. +/- shift
4. Posterior fossa mass
   1. Look for displacement/compression of 4th ventricle

Source

• NEJM 2001; 345; 1727-33
• Emergency Radiology: Case Studies Schwartz