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New Treatments for Brain Abscess and Neurologic Infections

Supratentorial neurosurgical infections. One is abscess, the second is epidural empyema, and subdural empyema, which statistically is not as common. Whenever you have infection in the supratentorial compartment hitting one side of the brain, always remember Herpes simplex encephalitis as the differential diagnosis.

Brain abscess. Look for local source of infection; ear, tooth, maybe skin, maybe trauma, maybe systemic. May be endocarditis, maybe IV drug use. If you look at the abscess pathologically or with MRI the pinnar surface is close to the ventricle. You need to remember that. So it kind of ruptures easily into the ventricle. Remember the wall is thinner on the ventricular side. What are the bugs? A whole bunch of them. Very often it’s more than one. Now for exam purposes let me just point out a couple here. If you have local trauma, staphylococcus is common.

If you have pus collection in the meninges, epidural or subdural, these people on the whole tend to be a little younger and seizures are more common. Seizures, in fact in my experience, are almost universal - if you are dealing with empyema - because they get a lot of cortico-thrombophlebitis so you have more irritation of the gray matter.

What about spinal abscess? Pretty uncommon, but differential diagnosis is humongous. Acute pain, paraplegia, you have to think all kinds of things. Especially the neurosurgeons in the audience. Before we get the MRI the problem may be metastases, the problem may be blood, spinal AVM. Maybe anticoagulants, obviously disc.

Shunt infection. Incidence, approximately 10% or less, higher after the first shunt. Higher in children, small children. Higher if the surgeon is less experienced. This is what the literature says. So these are the risk factors for shunt infection.

Bacterial meningitis. Strep, pneumonia, one out of four strep meningitis is now penicillin resistant. H. influenza B we don’t see anymore because of vaccination. Listeria is getting more common, especially in older people with meningitis. Strep pneumonia still carries very high morbidity and mortality. Neonates, strep pneumonia is now a number one cost. Listeria is becoming more common in the neonate. Morbidity seems to relate to cerebral edema and intracranial pressure.

If you have meningitis with trauma, post-op or shunt situation, make sure you are giving vancomycin. Now steroids in childhood meningitis is still a little bit controversial but I think most people now recommend a few days of steroids, especially children with meningitis. Especially if you happen to have H. influenza. Two, three or four days.

What about contacts for Neisseria meningitidis? Rifampin for a few days. Family members, school contacts. Rifampin is the way to go. For H. influenza Rifampin is for the contacts also. Here’s a list for strep, Neisseria, H. influenza, Listeria. Ampicillin. If you have a gram-negative situation a whole lot of different combinations there, including metronidazole. Proteus, Pseudomonas, gentamycin. Staph aureus, vancomycin.

Viral meningitis. Patients are less sick, no focal features. CSF shows lymphocytes, glucose is normal. Easy. Here is a list of some of the common causes you look for. Enteroviruses, echo, Coxsackie B, polio, mumps, Herpes simplex I and II, Varicella zoster, Epstein-Barre, adenovirus, lymphocytic choriomeningitis, occasionally Influenza A and B. Now the differential diagnosis of viral meningitis includes partly treated bacterial meningitis. Look for cultures, look for how sick the patient is, look for antigens.

Herpes simplex and TB. If you suspect Herpes simplex encephalitis, your differential is viral meningitis, obviously look at EEG. Start them on acyclovir but you can do PCR for herpes virus.

Fungal meningitis. Regional distribution is important. In the Southwest coccidioides is a common cause. If you have patients on hemodialysis, IV drug use, hyperalimentation, go for Candida first. In the Mississippi valley, with an abnormal chest x-ray, obviously go for TB.

In viral encephalitis, patients are more sick, altered mental status, focal findings, abnormal EEG. Herpes simplex of course. Eastern Equine: high morbidity. Western Equine encephalitis is more benign. Low morbidity. Outside the United States, Japanese and Venezuelan encephalitis is pretty common. Now all these are seasonal, mosquito-borne. Uncommon causes of encephalitis: Rocky Mountain Spotted disease, Lyme, Leptospirosis - this is very rare, very high mortality.

HIV. If your CD4 count is reasonable, an HIV patient is more likely to have stroke. He can have a meningitis. Now as the CD4 drops you go through TB and then AIDS-related dementia. Now when the count is very low you get PML, CMV lymphoma zoster. And crypto comes under here. So this is going to be of some practical use in differential diagnosis when you are dealing with these guys. There is no absolute rule here. CD4 is the lymphocytes that the AIDS virus affect, that destroy them. The clue for toxoplasmosis, very early focal signs.

Lymphoma: subacute onset. The lesions cross the midline then you find lesions close to the ventricles. The focal findings will be very similar to toxo sometimes but if MRI lesions cross the midline, think lymphoma. One you get toxo once, you are going to get it again. They need maintenance. Maintenance means maintenance for the rest of their life. You can look for Epstein-Barre PCR in the biopsy specimen, if the lesion is lymphoma. It’s not very sensitive but you may pick the virus particles in about 30 or 40% of lymphomas. If you are not sure between toxo and lymphoma, obviously you need to go for biopsy. Crypto: clues, retinitis. If the scenario is a patient with AIDS, low CD4 count, has some visual blurring and has headache, think crypto. Polyradiculitis is common. It can catch the cranial nerves. PML: you saw PML JC virus. Symmetric demyelination on MRI. PML lesions do not enhance. That’s important. PML lesions do not enhance. Toxo enhances, lymphoma enhances. Lymphoma crosses the midline. Zoster, myelitis is common. CMV can produce myelitis. CMV can produce myeloradiculitis. CMV can produce polyneuropathy. There are a whole bunch of differential diagnoses. Any one of them can produce myelopathy.

Slow viruses. Kuru, New Guinea, Creutzfeldt-Jakob, dementia, myoclonus, basal ganglia problems. Maybe cortical blindness, maybe ataxia, periodic complexes. The CSF is normal. They die in about a year, at the most two. PML we talked about. JC virus, white matter. What does this do? Gertsmann’s-Strausler syndrome? What’s the main sign and symptom? Cerebellar ataxia, positive family history. So the differential diagnosis for Creutzfeldt-Jakob in a way is Gertsmann’s-Strausler. But look carefully for family history. SSPE: post-measles, younger.