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Case 22-2005 — An 81-Year-Old Man with Cough, Fever, and Altered Mental Status
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     Presentation of Case

    Dr. Sherry Chou (Neurology): An 81-year-old man was admitted to the Massachusetts General Hospital in September because of fever, chills, productive cough, and diffuse weakness.

    Two weeks before admission, a cough developed, with small amounts of yellowish sputum. The patient was treated with azithromycin for five days, without improvement. Five days before admission, amoxicillin was begun. The cough continued to worsen, with increased production of sputum that was tinged with blood. High fevers and chills developed, with progressive anorexia, diffuse weakness, and mild confusion. He was brought to the emergency department and admitted.

    A diagnosis of chronic lymphocytic leukemia (CLL) had been made six years earlier. The patient had been treated for two years with fludarabine, which was stopped because anemia and thrombocytopenia had developed. For three years before admission, he received no treatment for his leukemia and had been clinically stable, with slowly rising peripheral lymphocyte counts and falling serum immunoglobulin levels (Table 1). He had had several episodes of viral and pneumococcal pneumonia in the two years before admission. Other medical problems included atrial fibrillation, diabetes mellitus, hypertension, prostatic adenocarcinoma (which had been treated with radiation therapy seven years earlier), multiple cutaneous squamous-cell carcinomas (treated with surgical excision), and three melanomas on the face and neck. The most recent melanoma had been treated within the six months before admission with excision and skin grafting.

    Table 1. Hematologic and Immunologic Laboratory Data.

    The patient lived at home with his wife in the Boston area. He had traveled to California six months before and to New York one month before becoming ill. He had no known contacts with sick people or recent exposures to animals or insects. He did not have nausea, vomiting, or a change in bowel habits. His medications on admission included potassium chloride, digoxin, hydrochlorothiazide, atenolol, warfarin, glyburide, and amoxicillin.

    On examination, the patient appeared tired but was able to converse appropriately. The axillary temperature was 39.6°C. The pulse was irregular at 100 beats per minute, the blood pressure 170/90 mm Hg, and the respiratory rate 24 breaths per minute. Oxygen saturation was 98 percent with the patient breathing 2 liters of supplemental oxygen delivered by nasal cannula. The pupils were equal and reactive to light. The neck was supple. There was no palpable cervical lymphadenopathy, but slightly enlarged lymph nodes were present in the axillae. The chest was clear to auscultation. There was a 2/6 systolic ejection murmur at the right upper sternal border. The abdomen was nontender, nondistended, and soft. The tip of the spleen was palpable. The remainder of the examination revealed no abnormalities. On neurologic examination, the patient was mildly confused and was not oriented to place or time. He did not follow commands. The strength in the arms and legs was 3/5 bilaterally. There was marked truncal weakness, and he was unable to sit up in bed.

    A chest radiograph showed prominence of the right paratracheal stripe and right hilum and bilateral small pleural effusions. Blood levels of electrolytes and serum levels of urea nitrogen, creatinine, glucose, albumin, bilirubin, alkaline phosphatase, and aminotransferase were normal. The amylase level was 106 units per liter and the lipase level 7.1 units per liter; the globulin level was 2.3 g per deciliter. Hematologic laboratory values are shown in Table 1. Flow cytometry of peripheral-blood lymphocytes revealed that they were CD19+ and CD20+ B cells coexpressing CD5 and CD23 and monotypic lambda immunoglobulin light chains. Specimens of urine, blood, nasal secretions, and sputum were sent for culture and viral testing. Ampicillin, gentamycin, and metronidazole were administered.

    On the second hospital day, the patient remained febrile, with a temperature that peaked at 39.1°C. He continued to be confused, and by the third day he was somnolent. His degree of arousal waxed and waned. Right-sided weakness developed. Computed tomographic (CT) scanning of the head after the administration of intravenous contrast material revealed no abnormalities except for mild mucosal thickening of the ethmoid air cells. CT scanning of the chest showed mediastinal and axillary lymphadenopathy that had enlarged since a study obtained five months earlier. There was no hilar lymphadenopathy or pulmonary abnormalities. A lumbar puncture was performed (Table 2). Flow cytometry showed that the lymphocytes were T cells (90 percent) with a normal immunophenotype and a normal CD4:CD8 ratio; there were a small number of B cells with an immunophenotype identical to that of cells associated with CLL.

    Table 2. Results of Cerebrospinal Fluid Analysis.

    Acyclovir and ceftriaxone were begun. On the fourth hospital day, the patient became progressively more somnolent, and hypoxemic respiratory failure developed (the partial pressure of oxygen was 63 mm Hg with the fraction of inspired oxygen at 40 percent). The trachea was intubated, and the patient was transferred to the medical intensive care unit. He had only minimal motor response to pain. He had a weak grimace in response to nasal tickle and a cough reflex. Nuchal rigidity was present. Repeated CT scanning of the head showed no changes. An abdominal ultrasonographic study showed no gallstones; the spleen was enlarged. A culture of sputum that had been obtained on the first hospital day grew Pseudomonas aeruginosa. The results of other laboratory tests are shown in Table 1, Table 2, and Table 3. Ceftriaxone was discontinued and ceftazidime was begun.

    Table 3. Microbiologic Test Results.

    By the fifth hospital day, the patient was comatose. Magnetic resonance imaging (MRI) of the brain showed a region of restricted diffusion in the left thalamus with surrounding T2 hyperintensity that involved most of the left thalamus. There was a 5-mm-long, enhancing focus, T1 isointense and T2 hyperintense, that was located just inferior to the left hypoglossal canal and thought to be a schwannoma. Magnetic resonance angiography showed mild irregularity, including foci of slight ectasia of the major cerebral arteries, that was consistent with atherosclerosis. Contrast-enhanced CT scanning of the abdomen and pelvis disclosed a small calcification in the spleen, multiple cysts in both kidneys, and an enlarged periaortic lymph node that measured 20 mm by 27 mm.

    Over the course of the next seven days, the patient remained comatose and unresponsive. A dose of intravenous immunoglobulin was given on the seventh hospital day. After discussion with his family, ventilator support was withdrawn on the 12th hospital day, and the patient died. An autopsy was performed.

    Differential Diagnosis

    Dr. Harry Hollander: May we review the imaging studies?

    Dr. Pamela W. Schaefer: Fluid-attenuated inversion-recovery images and T2-weighted images from the MRI examination performed on the fifth hospital day (Figure 1) show subtle hyperintensity throughout most of the left thalamus, with mild expansion. On diffusion-weighted images, there is a punctate focus of decreased diffusion within the left thalamus, but most of the left thalamus has relatively normal diffusion. No abnormal enhancement is seen.

    Figure 1. Magnetic Resonance Images on the Fifth Hospital Day.

    A fluid-attenuated inversion-recovery image (Panel A) and a T2-weighted image (Panel B) show subtle hyperintensity in the left thalamus (arrow, Panels A, B, and C). On the diffusion-weighted image (Panel C), there is a punctate hyperintense focus that suggests ischemia. Most of the left thalamus is relatively isointense to, and has diffusion similar to, the remainder of the brain parenchyma.

    The differential diagnosis for the left thalamic lesion includes viral encephalitis and bartonella infection, among other infectious and inflammatory processes, low-grade glioma, subacute arterial or venous infarction, paraneoplastic syndromes, and acute disseminated encephalomyelitis.

    Dr. Hollander: A central issue in framing the differential diagnosis in this case is the accurate characterization of the central nervous system syndrome.

    Defining the Neurologic Syndrome

    The presence of fever and the physical findings of meningeal irritation and cerebrospinal fluid pleocytosis all support the conclusion that a component of meningitis could be part of the syndrome under discussion. Perturbations of cognition and level of consciousness are often seen in patients with meningitis. However, altered mental status that precedes the onset of meningeal findings and worsens in the setting of relatively mild, stable abnormalities of the cerebrospinal fluid suggests that encephalitis is actually the primary process.

    The profound peripheral weakness that was observed in this patient cannot be explained on the basis of meningoencephalitis alone and suggests involvement of additional levels of the neuraxis. I assume that the weakness was hypotonic and that the respiratory arrest later in the course probably represented ventilatory failure caused by involvement of the respiratory musculature. A lesion in the cervical spinal cord would probably be accompanied by sensory changes and sphincter dysfunction. Polyradiculopathy tends to be asymmetric, often preferentially affects the lumbosacral plexus, and is characterized by mixed motor and sensory findings rather than isolated motor involvement. Patients with a demyelinating neuropathy often have pure motor findings, but typically, the cerebrospinal fluid does not show the degree of inflammation observed here. Thus, the most likely site of neuropathology that explains this degree of weakness is diffuse involvement of anterior horn cells, the ventral roots of the spinal cord, or both. In summary, this patient's clinical findings indicate a syndrome of meningomyeloencephalitis or encephalomyelitis, and this must be the focus of the differential diagnosis.

    Complications of CLL

    CLL usually follows an indolent, minimally symptomatic course for many years, as it did in this man. When a patient with this underlying diagnosis presents with new clinical problems, there are several types of complications that must be considered: autoimmune manifestations, direct effects of tumor infiltration or biologic transformation (Richter's syndrome), complications of treatment, and intercurrent infections.

    Most autoimmune complications of CLL are hematologic, with worsening thrombocytopenia or anemia as a result of autoantibody formation. Once hypogammaglobulinemia develops, autoimmune disease is a less likely explanation for new clinical complications. This patient's syndrome and the absence of radiographic findings indicating demyelination argue against an autoimmune cause for his problems. Finally, CLL is not a tumor associated with paraneoplastic autoimmune manifestations such as the anti-Hu syndrome.

    A more difficult issue is determining whether this patient's decline is a result of increasingly aggressive behavior or biologic transformation of the CLL. Progressive leukocytosis and hypogammaglobulinemia, increasing mediastinal and retroperitoneal lymphadenopathy, and, perhaps, the development of pleural effusions all raise the possibility of transformation to high-grade lymphoma (Richter's syndrome). The stable immunophenotype of the circulating leukemic cells argues against this, and tissue specimens must be obtained to establish the diagnosis of high-grade lymphoma. Unlike myeloid leukemias, CLL rarely produces intravascular leukostasis leading to organ-system dysfunction, even with extreme elevation of the peripheral white-cell count. Treatment complications are not an issue in this case, because the patient had received no recent therapy for CLL.

    Infections cause high morbidity and mortality in CLL. Early in the course of the illness, encapsulated bacteria, especially pneumococcus, may cause severe invasive disease because of hypogammaglobulinemia. With therapy, the incidence of viral infections, particularly herpesviruses, rises. Pulmonary infections are common, cause substantial mortality, and constitute a common indication for hospitalization. In the central nervous system, infection with the JC papovavirus may cause progressive multifocal leukoencephalopathy, but I will not consider this diagnosis further because of the rapid course, absence of typical imaging findings, and evidence of inflammation in the cerebrospinal fluid.

    In the patient under consideration, the absence of a typical mass lesion and the predominance of T cells in the central nervous system both strongly suggest that the neurologic syndrome is not a direct complication of CLL.

    Infectious Causes of Encephalomyelitis

    The causes of meningoencephalitis are legion and may have tremendous overlap in clinical presentation, laboratory results, and imaging findings, which can make diagnosis extremely difficult.1 In this patient, the presence of profound humoral immunodeficiency presents even greater diagnostic challenges, owing to the substantial likelihood of false negative serologic studies. Thus, the accurate etiologic diagnosis of encephalitis leans heavily on epidemiologic clues and unique clinical or radiologic findings.

    The presence of a poliomyelitis-like syndrome with flaccid paralysis should focus attention on viruses, which are the only pathogens likely to cause this syndrome, with or without concomitant encephalitis. Herpesvirus infections must be briefly considered because of the frequency with which these viruses cause encephalitis and because of the common association with late-stage CLL. Herpes simplex virus 1 (HSV-1) is probably not the cause of this man's encephalitis because there were no temporal-lobe abnormalities on imaging studies, and the negative results of the polymerase-chain-reaction (PCR) assay for HSV-1 in the cerebrospinal fluid. Both of these indicators have excellent negative predictive value.2,3 Varicella zoster may cause acute strokes or a chronic leukoencephalitis in immunocompromised patients,4 but neither pattern fits this clinical picture. Cytomegalovirus disease of the central nervous system is largely confined to patients with human immunodeficiency virus infection. Human herpesvirus 6 and human herpesvirus 7 most commonly cause encephalitis in recipients of transplanted stem cells. Moreover, none of the above viruses is commonly associated with a poliomyelitis-like illness.

    In the late summer and early fall, enteroviruses are a common cause of aseptic meningitis, and they can occasionally cause more severe neurologic disease, including encephalitis and flaccid paralysis. Enterovirus 71 has been associated with outbreaks of brain-stem encephalitis and flaccid paralysis in Asian children.5 Hypogammaglobulinemia may predispose patients to severe meningoencephalitis associated with enteroviruses. This predisposition is most commonly seen in children with X-linked hypogammaglobulinemia but has also been documented in adults with common variable immunodeficiency.6,7 PCR analysis of cerebrospinal fluid for enteroviruses has a sensitivity of more than 98 percent for detecting infection of the central nervous system.8 Thus, the negative cerebrospinal fluid study in this patient provided important evidence against this diagnosis. However, since enteroviral infection was still a possibility on clinical grounds, administration of intravenous immune globulin was justified, since this has been successfully used as adjunctive therapy in cases in which there is underlying immunodeficiency.

    Finally, arthropod-borne infection must be considered, given the season in which the patient presented, the greater likelihood of severe disease in elderly and immunocompromised patients, and the presence of several pathogens causing viral encephalitis in Massachusetts, including St. Louis virus, eastern equine encephalitis virus, Powassan virus, and West Nile virus. Of these, only West Nile virus has been reported to cause flaccid paralysis, either as an isolated neurologic manifestation or in conjunction with encephalitis. Lower motor-neuron weakness is reported in 20 to 60 percent of patients infected with West Nile virus that affects the central nervous system.9,10 The thalamic abnormality revealed on MRI of this patient adds weight to this diagnosis, because an increasing number of flaviviruses have been associated with basal-ganglion involvement.11 A parkinsonian syndrome developed in a minority of patients during or after recovery from West Nile encephalitis,10,11 attesting to the clinical relevance of the imaging findings. A respiratory prodrome is atypical of West Nile virus infection, however, and its presence makes me wonder whether it was due to an unrelated infection in this case.

    The best diagnostic test for West Nile encephalitis is generally a measurement of IgM antibody in the cerebrospinal fluid, which has a sensitivity of approximately 80 percent on the first sample.12 PCR-based assays of cerebrospinal fluid are less sensitive.13 The IgM measurement in the cerebrospinal fluid was negative in this patient, but I believe it was a false negative result caused by his hypogammaglobulinemia. There are no established therapies for severe West Nile infection, and supportive care is the cornerstone of management. Intravenous immune globulin has been given in some cases,14 but its efficacy is not known.

    Dr. Nancy Lee Harris: Dr. Singhal and Dr. Daskalakis, could you give us your impressions at the time that you cared for this patient?

    Dr. Aneesh Singhal (Neurology): When neurology consultants first saw this patient, he was intubated and comatose, and it was difficult to determine whether his weakness resulted from a central or a peripheral nervous system process. The history of fever, cough, and a rapidly progressive encephalopathy, along with the results of the cerebrospinal fluid studies, raised the possibility of a viral meningoencephalitis. Cerebral complications of chronic leukemia were considered unlikely for the reasons outlined by Dr. Hollander. The MRI finding of diffuse hyperintensity in the left thalamus was consistent with a viral encephalitis and has been reported in patients infected with West Nile virus, eastern equine encephalitis virus, and Japanese B encephalitis virus, as well as in bartonella, and in several other types of encephalitis. Given this patient's geographic location, we considered West Nile virus and eastern equine encephalitis virus infections to be the leading differential diagnoses. We thought that the small hyperintense lesion seen on diffusion-weighted imaging was a region of intense inflammation within the surrounding T2-hyperintense region of encephalitis, rather than an area of ischemia.

    Dr. Demetre C. Daskalakis (Infectious Disease): This patient's initial presentation was similar to that of many elderly patients with community-acquired infections, such as pneumonia or urinary tract infection. Though weakness and confusion may complicate such infections, the progressive confusion and weakness prompted a lumbar puncture that revealed a lymphocytic pleocytosis, suggesting meningoencephalitis or lymphomatous meningitis. Although the most common cause of viral meningoencephalitis is infection with herpes simplex virus, we considered this an unlikely cause for the reasons outlined by Dr. Hollander. We also considered partially treated bacterial meningitis, since both pneumococcus and meningococcus could have responded to azithromycin. Listeria infection of the central nervous system may cause a meningoencephalitis very similar to that from viral causes and may occur more frequently in patients with underlying hematologic cancer than in normal hosts. This patient's presentation in early autumn led us to consider arboviruses. The viral meningoencephalitis most associated with flaccid paralysis is West Nile virus. Central nervous system involvement by CLL or high-grade lymphoma was still being seriously considered by the clinical team caring for this patient at the time of his death.

    Clinical Diagnoses

    Viral meningoencephalitis due to enterovirus or West Nile virus infection.

    Alternate diagnosis: Central nervous system involvement by CLL or high-grade lymphoma (Richter's syndrome).

    Dr. Harry Hollander's Diagnosis

    Severe viral encephalomyelitis with flaccid paralysis, probably due to West Nile virus, with underlying hypogammaglobulinemia due to CLL.

    Pathological Discussion

    Dr. E. Tessa Hedley-Whyte: The postmortem examination revealed extensive replacement of lymph nodes, bone marrow, and spleen by CLL with focal infiltrates in the lung, kidney, liver, heart, and prostate gland. The mass in the hypoglossal canal was an accumulation of lymphoid cells, consistent with an infiltrate of CLL, with no sign of a schwannoma.

    The brain was externally and internally unremarkable on gross examination. Gross inspection of the spinal cord revealed congestion and retraction of the anterior horns, more marked in the cervical and lumbar areas and less so in the thoracic area. Microscopical examination of the brain and spinal cord revealed an extensive encephalomyelitis, with the most substantial damage in the anterior horns of the spinal cord and motor nuclei of the brain stem. Multiple areas of necrosis and inflammation were present, characterized by loss of neurons, accumulation of CD3+ lymphocytes and macrophages, and microglial nodules (Figure 2A through 2D). The thalamus, cerebellum, and cerebral cortex contained scattered microglial nodules (Figure 2E). Staining for the presence of infectious agents that might have caused encephalitis in an immunosuppressed patient, including toxoplasma, fungi, acid-fast bacilli, and Epstein–Barr virus, was negative.

    Figure 2. Microscopical Examination of the Brain and Spinal Cord at Autopsy.

    A cross-section of the cervical spinal cord (Panel A) shows a marked inflammatory infiltrate that is most severe in the anterior horn (delineated by arrows). At higher magnification (Panel B), there is marked destruction of anterior-horn neurons with perivascular lymphocytic cuffing seen at lower right of the panel. (The arrow indicates a remaining neuron.) The infiltrating cells in Panel C are CD3+ T cells (immunoperoxidase stain for CD3). A section of 12th nerve nucleus (Panel D) shows a microglial nodule (arrows) composed of macrophages and degenerating neurons being phagocytized (neuronophagia). A section of cerebellum (Panel E) shows focal infiltration by inflammatory cells (arrows) (Panels A, B, D, and E, hematoxylin and eosin stain). With the presence of antibody to the West Nile virus antigen, there is staining of neurons in the hippocampus (Panel F). The brown-colored reaction product fills the entire cytoplasm and dendrites of the positive neurons. (Immunoperoxidase stain for West Nile virus, Panel F, performed by Juan Bilbao, M.D., University of Toronto, Toronto.)

    Because the findings on admission included severe motor weakness, especially of the trunk, we thought that this condition might well be West Nile virus encephalomyelitis — despite the negative serologic assays. We sent unstained sections of the spinal cord, thalamus, and hippocampus to Dr. Juan Bilbao at the University of Toronto, who performed immunohistochemical staining for West Nile virus antigens.15 Clusters of neurons in the hippocampus and the thalamus were positive for West Nile virus antigens (Figure 2F). The spinal cord was negative except for an occasional neurite. These results established the diagnosis of West Nile virus encephalomyelitis. Cerebrospinal fluid obtained at postmortem examination was sent to the Massachusetts State Laboratory for testing for West Nile virus. The cerebrospinal fluid was positive for West Nile virus DNA by PCR, confirming the diagnosis of West Nile virus infection. The results of tests for antibodies to West Nile virus remained negative.

    The first report of West Nile virus encephalomyelitis in 199916 noted that the infected patients were weak, but since examination of the spinal cord is often omitted as a part of the routine autopsy, initial pathology reports did not recognize involvement of the spinal cord as the explanation for the weakness17; this phenomenon was later recognized and reported.18

    Twenty-three of 44 consecutive autopsy samples of the central nervous system submitted to the Centers for Disease Control and Prevention with a diagnosis of encephalitis between August and December 2002 tested positive for West Nile virus encephalitis.19 As in this case, underlying medical conditions were present in more than 80 percent of the patients, and 70 percent of the patients were men more than 70 years of age. The histologic abnormalities, as in this case, were primarily in the brain stem and the anterior horns of the spinal cord. Serologic assays for West Nile virus were positive in 18 of 20 cases tested. West Nile virus antigens were detected by immunohistochemical analysis in only about half of the cases — more often in cases tested within the first week of illness than in those tested later.

    Anatomical Diagnoses

    Encephalomyelitis due to West Nile virus.

    CLL with involvement of the lymph nodes, bone marrow, spleen, lung, kidney, liver, heart, prostate, and hypoglossal canal.

    Source Information

    From the Division of Infectious Diseases, Department of Medicine, University of California at San Francisco, San Francisco (H.H.); the Departments of Radiology (P.W.S.) and Pathology (E.T.H.-W.), Massachusetts General Hospital, Boston; and the Departments of Radiology (P.W.S.) and Pathology (E.T.H.-W.), Harvard Medical School, Boston.

    References

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    Cinque P, Bossolasco S, Lundkvist A. Molecular analysis of cerebrospinal fluid in viral diseases of the central nervous system. J Clin Virol 2003;26:1-28.

    Domingues RB, Fink MC, Tsanaclis AM, et al. Diagnosis of herpes simplex encephalitis by magnetic resonance imaging and polymerase chain reaction assay of cerebrospinal fluid. J Neurol Sci 1998;157:148-153.

    Kleinschmidt-DeMasters BK, Gilden DH. The expanding spectrum of herpesvirus infections of the nervous system. Brain Pathol 2001;11:440-451.

    Huang C-C, Liu C-C, Chang Y-C, Chen C-Y, Wang S-T, Yeh T-F. Neurologic complications in children with enterovirus 71 infection. N Engl J Med 1999;341:936-942.

    Misbah SA, Spickett GP, Ryba PC, et al. Chronic enteroviral meningoencephalitis in agammaglobulinemia: case report and literature review. J Clin Immunol 1992;12:266-270.

    Rudge P, Webster AD, Revesz T, et al. Encephalomyelitis in primary hypogammaglobulinaemia. Brain 1996;119:1-15.

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    Nash D, Mostashari F, Fine A, et al. The outbreak of West Nile virus infection in the New York City area in 1999. N Engl J Med 2001;344:1807-1814.

    Pepperell C, Rau N, Krajden S, et al. West Nile virus infection in 2002: morbidity and mortality among patients admitted to hospital in southcentral Ontario. CMAJ 2003;168:1399-1405.

    Solomon T, Fisher AF, Beasley DWC, et al. Natural and nosocomial infection in a patient with West Nile encephalitis and extrapyramidal movement disorders. Clin Infect Dis 2003;36:E140-E145.

    Petersen LR, Roehrig JT, Hughes JM. West Nile virus encephalitis. N Engl J Med 2002;347:1225-1226.

    Lanciotti RS, Kerst AJ, Nasci RS, et al. Rapid detection of West Nile virus from human clinical specimens, field-collected mosquitoes, and avian samples by a TaqMan reverse transcriptase-PCR assay. J Clin Microbiol 2000;38:4066-4071.

    Haley M, Retter AS, Fowler D, Gea-Banacloche J, O'Grady NP. The role for intravenous immunoglobulin in the treatment of West Nile virus encephalitis. Clin Infect Dis 2003;37:e88-e90.

    Bilbao JM, Chiasson D, Young B. West Nile virus encephalitis: pathology of seven cases. J Neuropathol Exp Neurol 2003;62:538-538.

    Outbreak of West Nile-like viral encephalitis -- New York, 1999. MMWR Morb Mortal Wkly Rep 1999;48:845-849.

    Sampson BA, Ambrosi C, Charlot A, Reiber K, Veress JF, Armbrustmacher V. The pathology of human West Nile virus infection. Hum Pathol 2000;31:527-531.

    Sampson BA, Nields H, Armbrustmacher V, Asnis DS. Muscle weakness in West Nile encephalitis is due to destruction of motor neurons. Hum Pathol 2003;34:628-629.

    Guarner J, Shieh W-J, Hunter S, et al. Clinicopathologic study and laboratory diagnosis of 23 cases with West Nile virus encephalomyelitis. Hum Pathol 2004;35:983-990.(Harry Hollander, M.D., Pa)