Physician Assistant Exam: How to Identify Brain Infections
The two big nervous-system infection types you need to be aware of for the Physician Assistant Exam (PANCE) are meningitis and encephalitis. These conditions can be fatal if not quickly recognized and treated. Not knowing about them for the PANCE can be fatal in another way.
Meningitis on the PANCE
Meningitis is an inflammation of the membrane that blankets the spinal cord and brain. Meningitis comes in two types: bacterial and aseptic. The two conditions have similar presentations, but the similarities end there.
Bacterial meningitis is fatal unless it’s quickly diagnosed and treated. Symptoms of bacterial meningitis include fever, headache, photophobia, and neck pain. On physical examination, you can see nuchal rigidity, Kernig’s sign, and Brudziński’s sign.
The key in diagnosis lies in the cerebrospinal fluid (CSF) total protein count. With bacterial meningitis, you see a high protein count, low glucose level, and leukocytosis with a neutrophilic predominance. The person also has an increased opening pressure.
Common causes of bacterial meningitis include Streptococcus pneumoniae, group B strep, and Neisseria meningitidis. You commonly see group B strep as a cause of meningitis in neonates. Listeria monocytogenes is a cause of meningitis in infants, the immunocompromised, and the elderly.
The treatment for bacterial meningitis involves antibiotics, including vancomycin and ceftriaxone (Rocephin). For someone with Listeria monocytogenes, the treatment is ampicillin. In addition, dexamethasone (Decadron) is used in conjunction with antibiotics to treat bacterial meningitis.
Unlike bacterial meningitis, aseptic meningitis isn’t usually fatal. The symptoms can mimic those of bacterial meningitis, but aseptic meningitis isn’t as severe. Causes of aseptic meningitis can be viral or secondary related to medications such as NSAIDs. Concerning the cerebrospinal fluid count, you usually see normal or near normal protein and glucose levels. The treatment is supportive.
Cryptococcal meningitis, caused by the yeast Cryptococcus neoformans, can occur in anyone, but it has a predilection for someone who is immunocompromised. For example, in someone with HIV, you may see this infection when the CD4 count is less than 200. The treatment includes strong antifungal medications, including intravenous amphotericin B (Fungilin). Another cause of meningitis is cancer, so it’s called (get ready) carcinomatous meningitis.
You’re evaluating a 65-year-old man who presents with a fever and a severe headache. His mental status is intact. On exam, his Kernig’s and Brudziński’s signs are positive. You obtain a lumbar puncture, which shows a cerebrospinal fluid glucose of 30 mg/dL and protein levels of 600 mg/dL. The cerebrospinal fluid opening pressure is increased. Which one of the following would you use for treatment?
(A) Acyclovir (Zovirax)
(B) Fluconazole (Diflucan)
(C) Ceftriaxone (Rocephin)
(D) Indomethacin (Indocin)
(E) Phenytoin (Dilantin)
The correct answer is Choice (C), ceftriaxone, because the cerebrospinal fluid findings indicate bacterial meningitis. Choice (A), acyclovir, is used in treating herpes simplex encephalitis. Choice (B), fluconazole, is used in the treatment of a fungal meningitis.
Choice (D), indomethacin, isn’t indicated here and in fact would be a cause of aseptic meningitis. Choice (E), phenytoin, isn’t indicated because the patient hasn’t had any seizure activity (although encephalitis can present with seizures, especially if the temporal lobe is affected).
When clinically treating someone with bacterial meningitis, vancomycin (Vancocin) is given in addition to ceftriaxone (Rocephin). In an older patient, or in someone in whom Listeria is suspected, ampicillin (Polycillin) is also added.
Encephalitis on the Physician Assistant Exam
Encephalitis is a nasty, nasty inflammatory and infectious process of the brain. Like meningitis, it can be fatal if not quickly diagnosed and treated. Common presenting symptoms of encephalitis include a change in mental status that can worsen quickly, fever, neck pain, and neuropsychiatric symptoms.
The most common causes of encephalitis are viral and vector-associated (for example, West Nile virus). Another viral form of encephalitis you should be familiar with is herpes simplex encephalitis (HSE), sometimes called herpesviral encephalitis. Here are a few key points about herpes simplex encephalitis:
The diagnosis can be confirmed by lumbar puncture and brain imaging. The MRI can show abnormalities in the temporal lobe.
The treatment for herpes simplex encephalitis is intravenous acyclovir (Zovirax).
Herpes simplex encephalitis is actually a meningoencephalitis. A change in mental status and seizure-like activity confirm the presence of accompanying encephalitis.