Investigations in Neurology

Question 1

What position should a patient be in for a lumbar puncture?

Answer 1

Lying on side, curled forward w/ knees up to chest
OR
Sitting forwards, curled into a pillow

Question 2

What is the anatomical landmark for a lumbar puncture?

Answer 2

Just above L4 (tops of iliac crest/intercristal plane)

Question 3

Describe the procedure of a lumbar puncture?

Answer 3

Place pt in lat recumbent position
Locate L4
Insert needle obliquely above L4, parallel to plane of spine, through interspinous ligament

Question 4

What are the indications for a lumbar puncture?

Answer 4

Diagnosis of meningitis/encephalitis
Diagnosis of SAH
Measurement of CSF pressure (idiopathic intracranial HTN)
Therapeutic removal of CSF (idiopathic intracranial HTN)
Intrathecal drug administration
Diagnosis of miscellaneous conditions (MS, neurosyphillis, Behcet’s)

Question 5

What are the contraindications to a lumbar puncture?

Answer 5

Suspicion of mass in brain/cord, raised ICP
Overlying/local infection
Congenital lesions in area (meningomyelocele)
Problems w/ haemostasis
   -platelets <40
   -clotting abnormalities
   -anticoagulation
Haemodynamic instability

Question 6

What are the potential complications of a lumbar puncture?

Answer 6

Post LP Headache (30%)
Dry Tap
Infection
Damage to spinal nn (weakness, paraesthesia)
Coning of cerebellar tonsils

Question 7

What are the features of a post LP Headache?

Answer 7

Onset w/i 24hrs, resolves over 2 weeks
Constant, bilateral, dull ache
Worse when upright
Treated w/ analgesics +/- blood patch

Question 8

What is CSF xanthochromia?

Answer 8

Yellowish discolouration of CSF
Caused by bilirubin from RBC breakdown
Indicates that there has been a SAH

Question 9

What can be used to diagnose SAH?

Answer 9

CT w/i 12hrs of headache onset (98%)

LP w/ CSF xanthochromia (2%)

Question 10

What are the CSF findings that accompany multiple sclerosis?

Answer 10

Moderately raised protein (<1g/L)
Up to 50 lymphocytes/mm3
Oligoclonal IgG bands on electrophoresis

Question 11

What are the advantages of CT?

Answer 11

Rapid procedure, simple for patient

Good for identifying haemorrhage/calcification

Question 12

What are the disadvantages of CT?

Answer 12

Ionising radiation

Question 13

What are the advantages of MRI?

Answer 13

Superior anatomical detail in brain

Does not involve ionising radiation

Question 14

What are the disadvantages of MRI?

Answer 14

Longer procedure, claustrophobic

Question 15

What are the contraindications to MRI?

Answer 15

Electrically/magnetically/mechanically activated implants
Implants containing ferrous metal
Bullets, shrapnel, metal FOB