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Bacterial infections of the nervous system manifest themselves in several ways, most of which are neurologic emergencies. This chapter reviews the classic syndromes of meningoencephalitis and focal infection (cerebritis or abscess) and the syndromes of neurosyphilis, tuberculosis, botulism, leprosy, Lyme disease, Whipple disease, rickettsiosis, diphtheria, and ventricular shunt infections.

A 62-year-old woman sought care in late summer for a 4-day history of upper respiratory tract symptoms, intermittent fevers, headache, and a 1-day history of disorientation, word-finding difficulties, and unsteady gait. Upon arrival to the emergency department, she had a witnessed seizure and was intubated because of increased lethargy. Her temperature was 39.4 °C, but she was otherwise hemodynamically stable. She had normal ophthalmoscopic examination findings and antigravity strength in all 4 extremities. Her deep tendon reflexes were brisk, but plantar responses were flexor. She had no rash. Cerebrospinal fluid analysis showed a normal glucose value, protein concentration of 82 mg/dL, and mixed pleocytosis. She had been hiking recently, but her family reported that there were no tick exposures or mosquito bites. Brain magnetic resonance imaging showed areas of T2 fluid-attenuated inversion recovery hyperintensity involving primarily the left thalamus and basal ganglia without definitive gadolinium enhancement. Both serum and cerebrospinal fluid were positive for immunoglobulin M antibodies to West Nile virus. The patient was diagnosed with West Nile virus encephalitis. After the seizure, the patient was treated with levetiracetam, and empiric antimicrobials were started for acute meningoencephalitis, along with adjunctive dexamethasone. Continuous electroencephalography was obtained because of the persistent encephalopathy and showed no evidence of subclinical seizures. The dexamethasone was stopped after 2 doses because of low suspicion for pneumococcal meningitis, and the antibiotics were discontinued after results of serum and cerebrospinal fluid cultures were negative for bacteria (48 hours). Acyclovir was stopped after the polymerase chain reaction results were negative for herpes simplex virus and varicella-zoster virus.

A 47-year-old woman with a history of relapsing-remitting multiple sclerosis (MS) receiving natalizumab therapy sought a second opinion regarding a recent diagnosis of secondary progressive disease. She was first diagnosed with multiple sclerosis 8 years earlier. While taking natalizumab, she was monitored for the development of antibodies to JC polyoma virus. Nine months before our evaluation, anti-JC polyoma virus antibodies became positive, with an increased index of 1.1. Given sustained remission, she was continued on natalizumab with increased surveillance and a plan to switch to a different disease-modifying therapy after 24 months. Five months later she noted subacute onset of slurred speech and right upper extremity incoordination. Over the next 4 months she continued to have clinical decline. On examination she had moderate ataxic dysarthria and right greater than left appendicular ataxia. She relied on a wheelchair for transportation and required 1-person assist to stand. Reflexes were brisk with bilateral Babinski sign. This patient with relapsing-remitting multiple sclerosis on natalizumab had a new subacute progressive cerebellar syndrome without radiographic evidence of disease activity. Repeated magnetic resonance imaging showed worsening cerebellar atrophy, right sided greater than left sided, and evolving T2 hyperintensity in the brainstem without enhancement or mass effect. JC polyoma virus polymerase chain reaction was positive. The patient was diagnosed with JC polyoma virus granule cell neuronopathy. Natalizumab was discontinued, and she was treated with 4 of 5 planned cycles of plasma exchange. After her 4th cycle, worsening symptoms developed. Magnetic resonance imaging showed gadolinium enhancement in the brainstem supportive of immune reconstitution inflammatory syndrome. She received high-dose intravenous methylprednisolone followed by a prednisone taper. Her disability progression stabilized. JC polyoma virus central nervous system infection, 1 of several infections reported among treated patients with multiple sclerosis, occurs almost exclusively in immunosuppressed patients, including those receiving disease-modifying therapy for multiple sclerosis.

A 52-year-old man is admitted to a neurosciences intensive care unit during winter for management of seizures requiring mechanical ventilation. Two days earlier he reported cough and myalgia. He was found seated on the couch with altered mental state and was minimally responsive. Upon arrival to the emergency department he was febrile at 38.8 °C and tachycardic. Complete blood cell count showed leukocytosis (11.1×109 cells/L, neutrophilic predominance). Computed tomography of the head showed an area of hypodensity in the left temporal lobe. During computed tomography, the patient had generalized convulsions requiring lorazepam, fosphenytoin, and levetiracetam, followed by initiation of a continuous midazolam infusion before seizures were controlled. He was started on broad-spectrum antimicrobials, including acyclovir, and a lumbar puncture was performed. Cerebrospinal fluid protein concentration was 196 mg/dL, and he had 10 white blood cells/µL with lymphocyte predominance. There was no hypoglycorrhachia. After 24 hours, the patient was weaned from the midazolam infusion and maintained on levetiracetam monotherapy. He was extubated but remained encephalopathic. Magnetic resonance imaging performed the day after admission demonstrated numerous T2 hyperintense lesions throughout both cerebral hemispheres including both mesial temporal lobes and right thalamus. Nasopharyngeal polymerase chain reaction was positive for influenza virus A, which was later typed further and identified as pandemic 2009 H1N1 virus. A diagnosis of influenza-associated encephalopathy/encephalitis was made. The patient was treated with oseltamivir, as well as high-dose intravenous methylprednisolone. His encephalopathy gradually improved. Repeated imaging at 3-month follow-up showed resolution of the previously seen abnormalities. His neurologic examination was normal. Postinfectious or parainfectious autoimmunity syndromes refer to neurologic signs and symptoms that develop during or after an infection but are not thought to be caused by direct infection of the nervous system.

Parasitic infections make up a small but important subset of central nervous system (CNS) infections. Although necessary to be considered in the comprehensive differential diagnosis for patients presenting with suspected neurologic infections, these conditions are particularly important in regions where parasitic infections are endemic and for immunocompromised patients. Among the most common parasitic infections of the CNS are neurocysticercosis, echinococcosis (hydatid cyst), toxoplasmosis, amebic meningoencephalitis, and cerebral malaria.

Background The Venereal Disease Research Laboratory (VDRL) test performed in cerebrospinal fluid (CSF) is considered highly specific for the diagnosis of neurosyphilis, but algorithms to diagnose neurosyphilis require positive syphilis serologic testing prior to obtaining CSF-VDRL. Inappropriate use of diagnostic tests depletes healthcare resources, and contributes to rising healthcare expenditures. CSF-VDRL has historically been improperly utilized; however there is no recent evaluation of its use in clinical practice. We aimed to quantify rates of appropriate CSF-VDRL testing, determine the CSF-VDRL false-positivity rate and describe causes of false-positive CSF-VDRL reactivity. Methods In this retrospective cohort study of three Mayo Clinic sites (Rochester, MN, Jacksonville, FL, and Scottsdale, AZ), we measured the rate of appropriate CSF-VDRL test utilization in patients with negative testing from January 1, 2011 to December 31, 2017. We then identified all patients with positive CSF-VDRL testing from January 1, 1994 to February 28, 2018, characterized true- and false-positive rates and described causes of CSF-VDRL false-positivity. Results Among 8,553 persons with negative CSF-VDRL results, testing was unnecessarily ordered in 8,399 (98.2%). The word “syphilis” or “neurosyphilis” appeared in the notes of only 1,184 (13.8%) individuals with a negative CSF-VDRL result. From January 1994 through February 2018, 33,933 CSF-VDRL tests were performed on 32,626 individual patients. Among 60 positive CSF-VDRL results, 41 (68.3%) were true-positives, 2 (3.3%) were indeterminate, and 17 (28.3%) were false-positives. Every patient with true-positive CSF-VDRL had positive serologic syphilis testing prior to CSF testing. All patients with false-positive CSF-VDRL results were inappropriately tested. Neoplastic meningitis was a common cause of false-positive CSF-VDRL results. Conclusion This is the first study in decades to review CSF-VDRL utilization for the diagnosis of neurosyphilis. Inappropriate use of CSF-VDRL testing for diagnosis of neurosyphilis remains problematic in clinical practice. Following recommended testing algorithms would prevent unnecessary testing, preserve resources, and minimize false-positive results. Disclosures All Authors: No reported disclosures

Retroviruses are a family of RNA viruses that replicate by reverse transcription. The family includes HIV and human T-lymphotropic virus. This chapter reviews neurologic manifestations of these retroviruses. A retrovirus in the genus Lentivirus, HIV has 2 forms, HIV-1 and HIV-2. HIV-1 is associated with the global AIDS pandemic, whereas HIV-2 causes an AIDS-like illness primarily in West Africa, although pockets of infection exist globally.

Viruses may cause acute, subacute, or, rarely, chronic infection of the nervous system. The most common acute syndromes of nervous system infections are meningitis and encephalitis, but viruses can also affect the spinal cord and the peripheral nervous system. Viruses can be classified in many ways. One classification scheme assesses the type of nucleic acid (DNA or RNA), whether it is double or single stranded, its sense, and its method of replication.