CT Scan Prior to LP

5. If CT is the first investigation, it should be preceeded by blood culture and IV antibiotics, and followed by LP if there is judged no risk for herniation on CT. [2]

6. Inability to see fundi (looking for papilledema, hemorrhages or loss of venous pulsations) should not be grounds for CT [3], however these findings in the fundi would prompt CT prior to LP.

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Empirical Antibiotic Therapy in Suspected Meningitis [4,5]

Birth to 4 wk:

· Ceftriaxone 100 mg/kg, + Gentamycin + Vancomycin 15 mg/kg q6h. No Dexamethasone

4 wk to 2 mo:

· Ceftriaxone 100 mg/kg, + Gentamycin + Vancomycin 15 mg/kg q6h. Dexamethasone 0.15 mg/kg q6h.

Child over 2 mo:

· Ceftriaxone 100 mg/kg (max 2 gm) + Vancomycin 15 mg/kg q6h (max 2 gm/day). Dexamethasone 0.15 mg/kg

Adult under age 50:

· Ceftriaxone 2 gm daily + Vancomycin 1 gram bid. Dexamethasone 10 mg. IV q6h.

Adult over age 50:

· Ceftriaxone 2 gm daily + Vancomycin 1 gram bid + Ampicillin 2 gm q6h (to cover L. Monocytogenes). Dexamethasone 10 mg. IV q6h.

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CT Scan Prior to LP

In Suspected Subarachnoid Hemorrhage (SAH)

1. SAH is the cause of only 1% of headaches.

2. With typical symptoms SAH is present in 12% of those with normal neurological exam and 25% of those with an abnormal exam. [6] In existing prospective studies, all patients with problems following LP had abnormal neurological findings. [7,8]

3. Opinion regarding risk of LP first is either anecdotal or extrapolated from patients with abnormal neurological exam. [9]

4. LP is most sensitive 12 hours after onset of symptoms, but should not be delayed until after that time. [10] A second LP, however, done after 12 hours, is necessary to optimize sensitivity. 50% of patients present after 12 hours. For those who present earlier, a decision must be made to for timely LP or CT in order to avoid delayed diagnosis.

5. Extravasated blood can disperse quickly, and may be undetectable on CT after 12 hours. [7]

6. Xanthochromia takes some hours to develop, and will be missed on visual analysis 50% of the time. [11] CSF spectrophotometry is recommended on negative fluid to improve sensitivity, but this is rarely available. [9]

7. Patients with an abnormal neurological exam require CT as a first step. CT will miss some cases, especially if delayed. LP must follow CT in suspect SAH if CT is non-diagnostic. [6]

8. High risk patients (see list) with negative CT and LP need neurovascular imaging. [6]

9. All patients who receive LP as primary investigation require close followup if this study is negative.

10. This “LP first” strategy for patients with lone acute sudden headache (LASH), and normal neurological exam has the potential to reduce unnecessary patient transfers without imparting additional risk in rural areas.

11. Several theoretical analyses [12,13] suggest lone acute sudden headache (LASH) without abnormal level of consciousness, neck stiffness, focal neurological findings or signs of increased ICP can have LP without CT. ACEP guidelines support this as a Level III recommendation. 70% of acute headache meets these criteria. Prospective studies are still needed.

12. Conclusion: CT for impaired LOC or abnormal neurologic exam. For all others:

· Bias for CT for early presentation (<12 hr)

· Bias for LP on late presentation (>12 hr)

· CT cannot exclude SAH without LP

· LP cannot exclude other mass lesions without CT

· Xanthochromia is missed in 50% without spectrophotometry

· Patient followup is important

· Selected high risk patients with negative studies need neurovascular imaging. [6]

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High Risk Factors for Aneurysmal SAH

Modified from Edlow et al. [6]

* Starred findings indicate patients at very high risk for aneurysm. Consult for neurovascular imaging should be obtained even if CT and LP are negative

Clinical History

Onset of headache abrupt and maximal at onset

Severity “worst in life” or very severe

First headache of this intensity; different from prior headaches

Associated signs and symptoms

Loss of consciousness*

Diplopia*

Seizure*

Focal neurological signs*

Epidemiologic Factors

Cigarette smoking

Hypertension

Alcohol (heavy use or recent binge)

Personal or family Hx of SAH*

Polycystic Kidney disease*

Heritable connective tissue diseases

Ehlers-Danlos syndrome

Pseudoxanthoma elasticum

Fibromuscular dysplasia*

Sickle-cell anemia

Alpha1-antitrypsin deficiency

Physical Findings

Retinal or subhyaloid hemorrhage*

Neck stiffness*

Any unequivocal neurological finding (focal or generallized)*

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Contrandications to LP

1. Skin infection near the site of LP

2. Suspicion of intracranial shift due to mass effect

3. Uncorrected coagulopathy

· OK to proceed if it is reversed

· Platelet count should exceed 50,000

· ASA not a contraindication, but adding clopidogrel increases risk. [14]

4. Acute spinal cord trauma

5. Condition mandating CT prior to LP

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Avoiding Post-LP Headache

1. Reduced incidence with smaller bore needles

2. Reduced incidence with atraumatic needles (Whitacre or Sprotte)

3. Entering the dura with the bevel facing up (in left lateral position) reduces tearing of dural fibres.

4. Use of the stylet when entering the dura and replacing it on needle withdrawal reduces incidence.

5. No correlation with amount of CSF withdrawn.

6. Lying flat post LP does not reduce incidence of headache.

7. Intravenous caffeine or an epidural blood patch using the patients’ venous blood helpful in treatment.

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Investigations

1. Always do a blood glucose in patients showing alteration of mental status. Never assume that hypoglycemia in children is the cause of altered mentation.

2. Opening and closing pressures should be done. Normal is 5-28 cm. water in left lateral decubitus. If pressures are high, collect fluid as usual, but institute immediate measures post-LP including mannitol, corticosteroids and hyperventilation.

3. CSF xanthochromia is best seen in comparison with a tube of water against fluorescent light.

4. Three tubes of fluid are collected.

· Tube 1 for gram stain and C&S

· Tube 2 for glucose and protein

· Tube 3 for cell count and differential

· Consider a 4^th tube for other studies

India ink or Cryptococcal Ag (Cryptococcus)

AFB or PCR for TB

Viral PCR (includes HSV, CMV, EBV, arbovirus)

VDRL

fungal culture

viral culture

PCR or antibody titers for Lyme disease

oligoclonal banding if suspect MS, SLE (3-4 ml)

5. Normal CSF values:

Study	Normal Value
Opening Pressure	5-28 cm H₂O
Appearance	Crystal clear
Xanthochromia	None
RBC's	5 per mm³
WBC's	5 per mm³
Glucose	60-70% of serum value
Protein	0.2 - 0.45 g/L
Gram Stain and C&S	Negative

6. CSF values in common disorders:

Study	Bacterial Meningitis	Viral Meningitis	SAH
Opening Pressure	Often elevated	Often elevated	Often elevated
Appearance	Clear to turbid	Often clear	Clear to bloody
Xanthochromia	Negative	Negative	Often present
RBC's	<5 per mm³	<5 per mm³	>50 per mm³
WBC's	Elevated. Many PMNs	Elevated. Many lymphs	Slightly increased
Glucose	Low	Normal	Normal
Protein	Elevated	Elevated	Elevated
Gram Stain	May show organisms	Normal	Normal

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References

1. Oliver WJ, Thomas CS, Kuhns LR. Fatal lumbar puncture: Fact versus fiction – An approach to a clinical dilemma. Pediatrics. 2003; 112(3): 174-176.

2. Hasbun R, Abrahams J, Jekel J, Quagliarello J. Computed tomography of the head before lumbar puncture in adults with suspected meningitis. NEJM 2001; 345(24): 1727-1733.

3. Archer BD. Computed tomography before lumbar puncture in acute meningitis: a review of the risks and benefits. CMAJ 1993; 148(6): 961-965.

4. Meningitis guideline. Royal Childrens Hospital Melbourne: Accessed Oct 24, 2007. Available from: file:///C:/Palm%20Topics/Lumbar%20Puncture/RMH%20Antibiotics%20Clinical%20Practice%20Guidelines.htm

5. Fitch MT, van de Beek D. Emergency diagnosis and treatment of adult meningitis. Lancet Infect Dis. 2007; 7:191-200.

6. Edlow JA, Kaplan L R. Avoiding pitfalls in the diagnosis of subarachnoid hemorrhage. NEJM 2000; 342(1): 29-36.

7. Wasserberg J, Barlow P. Lesson of the week: Lumbar puncture still has an important role in diagnosing subarachnoid hemorrhage. BMJ 1997;315(7122):1598-1599.

8. Hillman J. Should computed tomography scanning replace lumbar puncture in the diagnostic process in suspected subarachnoid hemorrhage? Surg Neurol. 1986;26(6):547-50.

9. Schull MJ. Lumbar Puncture First? An old test and a new approach to lone acute sudden headaches. CJEM 1999; 1(2): 99.

10. Gerber CJ. Lumbar puncture should not be delayed in subarachnoid hemorrhage. BMJ 1998; 317(7151):148.

11. Soderstrom CE. Diagnostic significance of CSF spectrophotometry and computer tomography in cerebrovascular disease. A comparative study in 231 cases. Stroke 1977; 8(5): 606-12.

12. Schull MJ. Lumbar puncture first: an alternative model for investigation of lone sudden acute headache. Acad. Emg. Med. 1999; 6(2): 131-136.

13. Mann D. The role of lumbar puncture in the diagnosis of subarachnoid hemorrhage when computed tomography is not available. CJEM 2002; 4(2): 102.

14. Paal P, Putz G, Gruber E, Le GTQ, Lemberger P. Subarachnoid hemorrhage after lumbar puncture in a patient receiving aspirin and clopidogrel. Anesth. Analg. 2006; 102:644-645.

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