The patient had a episode about 2 weeks prior to admission where she could not speak for 24 hours. It passed. Then a week later it returned and persisted for 5 days: confusion and speech that was mostly random words.

The pateint was admitted to the hospital.

Exam was negative except for the inability to produce coherent speech.

Screening labs were normal as was the exam: specifically no cerebellar, posterior column or pupillary abnormalities.

It was known at the time of admission that the peripheral RPR was 1:2048 and the CD4 was 140. The presumptive admitting diagnosis was tertiary syphilis.

But there were none of the classic physical findings of syphilis and the problem with HIV is Occam is of no help.

With a focal speech problem we were concerned there may be a secondary diagnosis: some mass lesion in the brain. I was worried more about toxoplasmosis than anything else so before the LP there was an MRI.

It looked textbook for HSV encephalitis. And the LP?

250 WBC, slightly elevated protein and slightly decreased glucose. No red cells.

More like syphilis than HSV. And the HSV PCR was eventually negative.

But can syphilis present like ‘x’ where ‘x’ equals HSV. Of course it can. It’s syphilis. Virtually any disease can be substituted for ‘x’. But I looked in PubMed to make sure. Yep.

We report a case of neurosyphilis with magnetic resonance imaging (MRI) brain scan findings compatible with a diagnosis of herpes simplex encephalitis with negative testing for herpes simplex virus in the cerebral spinal fluid. An extensive review of the literature has been undertaken revealing 24 cases worldwide where there are mesiotemporal changes on MRI concurrent with a diagnosis of neurosyphilis. Therefore, it is now well established that neurosyphilis, ‘the great imitator’, should be considered in the differential diagnosis in all patients demonstrating mesiotemporal changes on MRI, changes usually seen in herpes simplex encephalitis.



I have to admit that if the patient presented with the above clinical signs and symptoms and the MRI but no pre-existing RPR I really doubt I would have made the diagnosis of syphilis with alacrity. I would have called it HSV encephalitis and puzzled over the negative PCR and worried it was a tumor or some other process. The patient probably would have gone on to brain biopsy. Good thing someone had already ordered the RPR.

The above abstract says it all: consider the ‘the great imitator’.

Rationalization

J S C Med Assoc. 1998 Jul;94(7):315–7. Neurosyphilis mimicking herpes simplex encephalitis. http://www.ncbi.nlm.nih.gov/pubmed/9689783

Intern Med J. 2012 Sep;42(9):1057–63. doi: 10.1111/j.1445–5994.2012.02829.x. Mesiotemporal changes on magnetic resonance imaging in neurosyphilis. http://www.ncbi.nlm.nih.gov/pubmed/24020346

For you youngsters, Rich Little: https://www.youtube.com/watch?v=78sSn3E_Vvc