MENINGITIS
ACUTE BACTERIAL MENINGITIS
Definition: Bacterial infection of the subarachnoid space
Microbiology:
S. pneumoniae is the most common cause in adults followed by N. meningitidis and H. influenza. Listeria can be seen in the elderly, alcoholics, or patients with immunosuppression or malignancy. GNR and staph infections are rarer, they are usually a nosocomial or post-procedural infection (ie: after neurosurgery) but again must be kept in mind when dealing with an immunocompromised patient.
Clinical Manifestations
-fever
-headache, stiff neck and photosensitivity
-altered mental status
-seizures
-2 out of 4 of these symptoms will be present in 95% of patients presenting with meningitis however keep in mind that the elderly and immunocompromised (ie: HIV+) may have an atypical presentation with lethargy and confusion as their primary symptoms and no fever
Physical Exam
-nuchal rigidity, kernig’s and brudzinski’s sign
-focal neuro findings
-fundoscopic findings (papilledema, absent venous pulsastions)
-rash: maculoapular, petechial or purpuric (may be associated with N. Meningitidis)
Diagnostic Studies
-blood cultures
-LP with gram stain and culture; consider a head CT to r/o mass effect before performing an LP if there is a presence of high-risk features (age >60, immunocompromised, h/o CNS disease, new onset seizures, altered mental status or focal neurological findings). However it should be noted that in pts with mass effect herniation may occur even without LP and may not occur even with LP.
CSF Findings in Meningitis:
| Condition | Appearance | Pressure | WBC/mm3 Predom type | Glucose | Protein |
| Normal | Clear | 9-18 | 0-5 lymphs | 50-75 | 15-40 |
| Bacterial | Cloudy | 18-30 | 100-10,000 polys | <45 | 100-1000 |
| TB | Cloudy | 18-30 | <500 lymphs | <45 | 100-200 |
| Fungal | Cloudy | 18-30 | <300 lymphs | <45 | 40-300 |
| Aseptic | Clear | 9-18 | <300 polys -> lymphs | 50-100 | 50-100 |
Treatment of Meningitis:
-For normal adults, empiric treatment consists of ceftriaxone 2g IV q12h +/- ampicilliln 2g IV q4h for Listeria.
-Consider adding dexamethasone 10mg IV q6h x 4 days as it is associated with a reduction in neuro disability and mortality in patients with S. pneumo and a GCS 8-11. It must be started before or with the first dose of antibiotics.
-If the patient is HIV positive or you have any suspicion that they are HIV + you may have to broaden your empiric coverage dramatically. Continue ceftriaxone to cover for bacterial meningitis but also consider ampicillin to cover for listeria, fluconazole to cover for cyrpto, acyclovir to cover for HSV or VZV, anti-TB meds to cover for TB meningitis (see TB lecture for details). You may also want to consider treatment for cerebral malaria, toxo, neurosyphillis.
ASEPTIC MENINGITIS
Definition: Negative bacterial microbiologic data, CSF with pleocytosis with – blood and CSF cultures.
Etiologies:
-Viral: enterovirus, HIV, HSV, VZV, mumps, viral encephalitis, adenovirus, polio, CMV, EBV
-Tuberculosis
-Parameningeal focus of infection (ie: brain abscess, epidural abscess, septic thrombophlebitis of dural venous sinus)
-Fungal, spirochetal, rickettsial
-Partially treated bacterial meningitis
-Medications: bactrim, nsaids, pcn, INH
-Systemic illness: SLE, sarcoid, Bechet’s, Sjogrens, RA
-Neoplasms: intracranial tumors, lymphomatous or carcinomatous meningitis
Empiric Treatment:
-no abx if suspect viral etiology (unless you suspect HSV/VZV); otherwise start empiric antibiotics and wait for the CSF culture data
-anti-TB meds if suspect TB meningitis
MENIGITIS CASE
You are the admitting intern for the following patient:
50 year old female is brought to Bugando Medical Centre by her husband because of confusion. She was well until the day before when she had complained of headache and malaise. On the day of admission, her husband reports she was disoriented and difficult to arouse and brings her into the hospital.
PMH: Hypertension. IDS status unknown
Meds: Aprinox 5 mg daily
Allergies: NKDA
SH: works in local restaurant. No alcohol. No cig smoking. No illicit drug use
FH: non-contributory
PE:
General:Somnolent. Arousable to voice.
Vitals:T=40°C P110 BP 100/70 oxygen saturation=96% on Room Air
Neck: ?nuchal rigidity
Chest: CTA b/l
CV: tachycardic. No murmurs
Abd: +BS. Soft nt/nd
Ext: no edema
Neuro: Somnolent. Oriented x 2 (knows name, location. not year). Cranial nerves intact. Moves all extremities. Normal reflexes. Babinski reflex downgoing
Questions:
1) What is most concerning about this patient’s vital signs? (High fever)
2) List your differential diagnoses. (Bacterial meningitis, viral meningitis/encephalitis, subarachnoid hemorrhage, stroke, drug overdose)
3) Name additional physical exam findings that are essential in evaluating this patient? (ophthalmologic exam, close examination of skin for rash)
4) What should be your immediate next step in management in this case? (CT of head if available, lumbar puncture, blood culture, antibiotics for bacterial meningitis)
5) Would your management change if you knew the patient was HIV+? (yes, would have a higher suspicion for cryptococcal meninigitis and therefore start high dose fluconazole)
