Understanding Herpes Simplex Encephalitis

Female Speaker: Lesson 11, Herpes simplex encephalitis, Script One. Dr. Brown: Good Morning, Dr. Oishi. Dr. Oishi: Good Morning, Dr. Brown. You were on duty last night, weren't you? Dr. Brown: Yes. I had an emergency admission last night. Dr. Oishi : Tell me about the case. Dr. Brown: The patient is a 20-year-old woman who noticed a fever and a headache three days ago. Two days ago, she went to a local doctor and got antibiotics. Last night, she became confused and her parents brought her to the emergency room. Dr. Oishi: What did you find on physical and neurological examination? Dr. Brown: Body temperature was 39.O C. She was confused and disoriented as to time, place and person. She had a stiff neck and the Kernig's sign was positive. The rest of the physical and neurological examination was normal. Dr. Oishi: Did you perform a lumbar puncture on her? Dr. Brown: Yes. The opening pressure was 250 mmCSF, cells 150/mm3, predominantly lymphocytes, protein 100 mg/dL, and glucose 60 mg/dL. Dr. Oishi: What was blood glucose at the time of the lumbar puncture? Dr. Brown: I didn't measure the blood glucose. Dr. Oishi : Well, you see if the blood glucose is 100, a CSF glucose of 60 is normal, but if the blood glucose is 200, a CSF glucose of 60 is abnormal. Dr. Brown: I didn't know that. Starting next time, I'll measure the blood glucose too. Dr. Oishi: Did you Gram stain the CSF? Dr. Brown: Yes, but no microorganisms were seen. Dr. Oishi: What do you think she has? Dr. Brown: I think she has meningitis. Dr. Oishi: What kind of meningitis? Dr. Brown: Viral meningitis is the most likely diagnosis, but we should also consider tuberculous meningitis and fungal meningitis. Dr. Oishi: What tests do you plan? Dr. Brown: I requested blood and urine tests, chest X-rays, a tuberculin test, a CT scan of the head and an EEG. Dr. Oishi: What treatment did you start? Dr. Brown: I started a drip infusion of glycerol and three liters of oxygen. Dr. Oishi: Is she on antibiotics? Dr. Brown: No, I discontinued it because the CSF findings were different from those of bacterial meningitis. Dr. Oishi: CSF findings were different between untreated bacterial meningitis and partially treated bacterial meningitis. The CSF findings of this patient are compatible with partially treated bacterial meningitis. Dr. Brown: Should I start antibiotics? Dr. Oishi: Yes. We had better use antibiotics until bacteria meningitis is ruled out. Dr. Brown: What is your impression? Dr. Oishi: My impression is herpes simplex encephalitis. In order to confirm the diagnosis, we need to measure the viral antibody titers in the serum and the CSF. Dr. Brown: I heard that a brain biopsy is used for the diagnosis of herpes simplex encephalitis in the USA. Dr. Oishi: That's true, but instead of a brain biopsy, an ELISA is used for the diagnosis of herpes simplex encephalitis in Japan. Dr. Brown: What does ELISA stand for? Dr. Oishi:ELISA stands for enzyme-linked immunosorbent assay. Dr. Brown: What is the major difference between the ELISA and conventional methods such as hemagglutination inhibition, complement fixation and the neutralization test? Dr. Oishi: The conventional methods take about three weeks to make a diagnosis but the ELISA only takes about two weeks. Dr. Brown: Do we have to wait for two weeks to make a diagnosis? Dr. Oishi:No. A viral antibody titers are for confirming the diagnosis. A presumptive diagnosis can be made by symptoms and signs, CSF findings, a CT scan, and an EEG. Dr. Brown: I will get a CT scan and an EEG as soon as possible. Dr. Oishi: When you get the results of those tests, let's discuss this case again. Female Speaker: Script 2. Dr. Brown: Hello, is this the CT room? John: Yes. Dr. Brown: Is John there? John: Speaking. Dr. Brown: Hi, John. This is Dr. Brown speaking. John: Hi, Dr. Brown. Dr. Brown: Will you do me a favor? I have a case for an emergency CT scan. Can you do it right now? John: Well, right now, I'm doing a CT scan on another patient, but I'll be finished in about 20 minutes. Bring your patient down in 20 minutes and I'll be ready for you. Dr. Brown: Thank you very much. Female Speaker: 20 Minutes later at the CT room. Dr. Brown: I brought my patient. John: Is she cooperative? Dr. Brown: No, she is confused. John: Please help me move the patient from the stretcher to this bed? Dr. Brown: Okay. John: Can she stay still? Dr. Brown: No. John:I think she needs sedation. Dr. Brown: I'll inject diazepam. John: Thanks. That'll let us get a good scan. Female Speaker: Script 3. Dr. Brown: I got the CT scan of the head and the EEG. Let's see the CT scan first. The plain CT scan shows a low density area in the right temporal lobe. The enhanced CT scan shows a linear enhancement in the right temporal lobe. Dr. Oishi: I agree with you. What do you think from this CT scan? Dr. Brown: This suggests herpes simplex encephalitis, but is also compatible with cerebral infarction. Dr. Oishi: Does she have any cardiac murmur or higher erythrocyte sedimentation rate? Dr. Brown: No. She doesn't have any risk factors for cerebral infarction. Dr. Oishi: All right. Now, let's see the EEG. Dr. Brown: The background activity is 7 Hz. Paroxysmal bursts of sharp waves and slow waves are seen over the right hemisphere. Dr. Oishi: Yes. These are called periodic lateralized epileptiform discharges and are seen in herpes simplex encephalitis and in cerebral infarction. Dr. Brown: We can rule out cerebral infarction from the clinical presentation and the CSF findings. Dr. Oishi: These laboratory findings and her clinical of course strongly suggest herpes simplex encephalitis. Dr. Brown: Should we start Ara-A? Dr. Oishi: There is a paper saying that Acyclovir is better than Ara-A for the treatment of herpes simplex encephalitis. Let's use Acyclovir. Dr. Brown: I see. Thank you for the discussion.