Stealth Viral Encephalopathy: Report of a Fatal Case Complicated by Cerebral Vasculitis

Pathobiology, S. Karger AG, 1996, Vol. 64, 59-63


A patient presenting with a severe subacute encephalopathy was shown to be infected with a stealth virus. Although the patient partially recovered, he remained lethargic with cognitive impairment and worsening headaches. Ten months after the onset of his illness, his clinical condition further deteriorated with seizures, coma and death. A brain biopsy revealed vacuolated degenerate neural cells consistent with a stealth viral encephalopathy. Focal perivascular lymphocytic inflammation was present within the leptomeninges and to a lesser extent within the parenchyma of the brain. Vasculitis may occasionally contribute to the complex symptomatology of stealth viral encephalopathy.


Specialized viral cultures and sensitive molecular probe based assays have identified stealth viral infections in patients with a wide range of neuropsychiatric dysfunctional brain disorders (information available at URL The spectrum of diseases seen in stealth viral infected patients probably reflects the intensity and predominant localization of infection occurring within the brain. It may also be affected by secondary autoimmune responses directed against neural antigens, and by indirect effects on blood supply resulting from involvement of the brain's blood vessels. This paper describes the clinical and histological findings seen in a patient in whom a stealth viral infection was complicated by cerebral vasculitis.

Case Report

The 33 year old Hispanic male was an outgoing, energetic individual working as a laborer. He had no prior significant medical history. Over a two week period in July 1993, he lost his appetite, complained of headaches and became depressed, irritable and reclusive. The day before hospital admission, he refused to eat, barely spoke and, what was said, was incoherent to his family. He became non-cooperative and only reluctantly was persuaded to come to the Emergency Room of the Los Angeles County Hospital. He was considered to have a psychiatric illness but was admitted, under restraints, to a Medical Ward to "rule out organic disease". Although he was fully conscious when admitted, he became more somnolent over the next several days and progressed into coma. There were no localizing neurological signs. The patient was treated empirically with Amphotericin B, flucytosine and acyclovir. Initial and subsequent CSF examinations were traumatic but indicative of a significant pleocytosis. The CSF white blood cell (wbc) counts per cu mm were 128 on the day of admission; and 169, 60 and 17 on days 7, 12 and 19 post admission. Polymorphonuclear (PMN) cells were seen on the samples collected on the day of admission and at day 7, constituting 29% and 7%, respectively, of the total wbc. At the time of admission, his peripheral blood wbc count was 11,900 with 77% PMN. The CSF protein level was 61 mg/dl on the day of admission (normal upper limit 50 mg/dl) and within normal limits at the other times of collection. His CSF IgG level was measured on the sample collected on day 19 post admission and was slightly elevated (36 mg/dl). Moreover, electrophoresis showed weak but discernible oligoclonal banding (data not shown). CSF glucose levels were normal at each time point. He had an elevated erythrocyte sedimentation rate of 28 mm (normal upper limit 20 mm) and a 1:40 anti-nuclear antibody titer showing a speckled pattern. The patient was HIV negative. CSF cultures for fungal organisms, acid fast bacilli and conventional viruses gave negative results. Magnetic resonance imaging (MRI) was performed at 5 and at 19 days post admission. Both studies showed multiple areas of abnormal high signal intensity within basal ganglia (fig. 1). These changes were seen in the T2 weighted, but not in the T1 weighted images. There was no meningeal enhancement. An EEG was interpreted as indicative of a mild encephalopathy consistent with a toxic, metabolic or infectious etiology. Specifically, it showed diffuse slow wave activity in the background plus intermittent polymorphic delta activity and occasional sharp waves over both temporal regions, mostly on the right side.

Polymerase Chain Reaction studies

As shown in Figure 2, a weak positive reaction was seen in a PCR assay performed on the patient's CSF using a human cytomegalovirus (CMV) primer set and probe. The primers used were originally designed to amplify a region of the CMV UL 83 gene (pp65 protein coding gene) between nucleotides 119,422 and 119,560 of the AD169 strain of CMV [1]. Under low stringency PCR conditions, these primers yield weak positive responses with other herpesviruses, including herpes simplex virus (HSV), human herpesvirus-6 (HHV-6), varicella zoster virus and Epstein-Barr virus [2]. The primers have been used to detect a subset of stealth viruses [2,3 and unpublished data]. The CSF sample gave a negative result using PCR primers reactive with the immediate early (I-E) gene of CMV [1] and with a primer set reactive with HSV (fig. 2).

Specialized blood cultures [4] were undertaken to test for the presence of a stealth virus. A vacuolating syncytial cytopathic effect (CPE), typical of that induced with other stealth viral isolates [4], developed on MRC-5 human fibroblasts, rhesus monkey kidney cells and Sf9 insect cells. The infected cells did not stain with antisera specific for human CMV I-E antigen [4] Anomalous PCR products were, however, generated from the infected cultures using the broadly reactive CMV primers in a low stringency PCR assay (data not shown). A CSF cytology sample, obtained 2 days after admission, was reexamined. Small clumps of atypical cells with foamy, vacuolated cytoplasmic changes were identified (fig. 3).

The patient's mental and physical condition gradually improved over the 3 weeks he spent within the County Hospital. He was transferred to a convalescent hospital where he continued to slowly improve over a 10 week period. He was discharged to the care of his family and instructed to report for out-patient rehabilitation therapy. The rehabilitation service, however, considered that he was mentally too disabled to benefit from therapy and advised him to wait for a more complete recovery. There was little or no improvement over the ensuring months. The patient showed little interest in outside activities and complained of severe fatigue, nervousness, increasing headaches and more generalized aches and pains. He slept for several hours each day and his major activity was to watch television without much comprehension. His memory of the days events was impaired and he communicated poorly with his family. Ten months from the onset of his initial illness, his clinical condition acutely deteriorated. He no longer spoke to family members and one day became extremely listless and in apparent pain. The next morning he developed a generalized tonic-clonic seizure lasting 10 minutes which was controlled by Valium administered by paramedics. He was transported unconscious to a community hospital. The patient was comatose with residual contractions involving both eyelids. His CSF contained 17 erythrocytes, 21 wbc (76% lymphocytes, 13% polymorphs and 11% monocytes), protein 68 mg/dl and glucose 61 mg/dl. Two subsequent CSF taps showed no abnormalities. An MRI examination was reported as normal while a second MRI showed minimal evidence of cerebral atrophy and unremarkable minor aberrations in periventricular regions. No localizing signs were found on neurological examination. The patient awoke the next day but was aphasic and non-responsive to attempted communications. His muscle tone was increased and although there was no voluntary movement, he would move in response to pain. His pupils responded sluggishly to light and his gag reflex was intact. Because of the prior history of probable encephalitis, a right temporal lobe brain biopsy was performed. The patient never regained consciousness and died in asystole two weeks after admission. An autopsy was not performed.

The brain biopsy showed a moderate, but patchy, periventricular lymphocytic inflammation affecting several of the blood vessels within the leptomeninges (fig. 4). The vasculitis was non-granulomatous and not associated with fibrinoid degeneration or hemorrhage. A small number of the blood vessels within the brain were also infiltrated with mononuclear cells (fig. 5). The larger blood vessels were generally only focally affected with nearby blood vessels remaining involved (fig. 6). There was essentially no inflammation extending from the focal vasculitis into the parenchyma of the brain. Many of the neuronal cells showed evidence of a cytopathic effect with distorted nuclei and fine vacuolating cytoplasmic changes (fig. 7)(fig. 8). Electron microscopy was not performed.


Viruses which can induce vacuolated foamy cell changes in fibroblast and kidney cell cultures, have been cultured from patients with a wide spectrum of neurological and neuropsychiatric disorders [3-6]. Support for an etiological role in these diseases has been provided by the demonstration of similar cellular changes in the brain of virus inoculated cats [7] and in the brains of severely ill, viral culture positive, patients [6]. These in vivo changes occurred in the absence of the marked inflammatory changes that normally accompanies herpesviral encephalitis. Indeed, the paucity of inflammation led to the suggestion that the atypical viruses lacked the major immunogenic components required for effective T cell immunity. These viruses were provisionally termed "stealth" because of their apparent ability to avoid effective immunity in vivo, and because they were not being recognized using conventional viral culture procedures. Molecular studies have shown that some of the stealth viruses are derivitives of herpesviruses, most notably African green monkey CMV [8]. Sequencing studies have not been performed on the virus isolated from the patient described in this paper.

This patient is reported primarily because of the histologic evidence of an appreciable vasculitis, especially affecting leptomeningeal blood vessels. This finding was in addition to the characteristic distorted nuclear and vacuolated cytoplasmic changes seen in many of the neural cells. The vasculitis was not suspected clinically nor indicated by the MRI examinations conducted during the final hospital admission [9].

Cerebral vasculitis can occur in association with many types of viral infection [10] and may be explained by several mechanisms, including: i) Egress of cells from the vasculature into the tissues in response to immunogenic viral or modified self antigens expressed on viral infected parenchymal cells. ii) Response to antigen-antibody complexes formed between circulating antibodies and the viral antigens diffusing from the infected tissue. iii) Direct viral infection of the blood vessel causing a disruption of the endothelial barrier function preventing lymphocyte adhesion and invasion. The patchy nature of the vasculitis and the involvement of varying sized blood vessels tend to argue against major roles for the first two mechanisms. CMV has a propensity to infect blood vessels [11] and certain stealth viruses might be expected to show the same potential.

Cerebral vasculitis is commonly diagnosed, with or without angiographic confirmation, on the basis of recurrent seizure activity, headaches and transient neurological deficits [9]. Clinically, it often responds to steroid and/or anti-metabolite therapy such as cytoxan or methotrexate [12]. Although a vasculitis is not a necessary component of stealth viral infection, it does help explain the seizure which led to the patient's final hospitalization. Earlier vascular changes may also explain the rather striking basal ganglia MRI findings seen on the initial hospitalization. The potential contribution of an accompanying vasculitis to severe stealth viral infections is currently being addressed in other patients.


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7. Martin WJ, Glass RT: Acute encephalopathy induced in cats with a stealth virus isolated from a patient with chronic fatigue syndrome. Pathobiology 1995; 63: 115-118.

8. Martin WJ, Ahmed KN, Zeng LC, Olsen JC, Seward JG, Seehrai JS: African green monkey origin of the atypical cytopathic "stealth virus" isolated from a patient with chronic fatigue syndrome. Clin Diag Virol 1995;4:93-103.

9. Harris KG, Tran DD, Sickels WJ, Cornell SH, Yuh WTC: Diagnosing intracranial vasculitis. The roles of MR and angiography. Am J Neuroradiol 1994;15:317-330.

10. Jennette JC, Falk RJ: Update on the pathobiology of vasculitis. Mongr Path 1995;37:156-172.

11. Golden MP, Hammer SM, Wanke CA, Albrecht MA: Cytomegalovirus vasculitis. Case reports and review of the literature. Medicine 1994;73:246-55.

12. Calabrese LH, Duna GF: Evaluation and treatment of central nervous system vasculitis. Curr Opin Rheumat 1995;7:37-44.


I wish to thank Drs. P. Colleti and S. Martin for the MRI and CSF cytology photographs.

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