Neuroinfections: Presentation, Diagnosis, and Treatment of - PDF document

Neuroinfections: Presentation, Diagnosis, and Treatment of Meningitis and Encephalitis Authors: *Kaitlin M. Bowers, 1 Vishnu V. Mudrakola 2 1. Hilton Head Hospital, Hilton Head Island, South Carolina, USA 2. Licking Memorial Hospital, Newark, Ohio, USA *Correspondence to Kaitlin.M.Bowers@gmail.com Disclosure: The authors have declared no confmicts of interest. Received: 11.03.20 Accepted: 06.05.20 Keywords: Anti-NMDA receptor encephalitis, bacterial meningitis, encephalitis, herpes simplex virus encephalitis, meningitis, neuroinfections, opportunistic infections. Citation: EMJ Neurol. 2020;8[1]:93-102. Abstract Neuroinfections cause signifjcant morbidity, mortality, and long-term disability. These infections rarely present with the classic signs and symptoms taught in textbooks. Due to the similarities in presentation between neuroinfections and many other disease processes, delayed diagnosis is common. Thus, it is important that care providers have a high clinical suspicion for potential cases because early diagnosis and treatment can signifjcantly improve outcomes. This article serves as a review of the approach to a patient with suspected neurological infection with an emphasis on clinical presentation, diagnosis, and treatment of the major causes of meningitis and encephalitis. Additionally, patients in an immunocompromised state are vulnerable to a whole host of additional neuroinfections that present atypically and will also be addressed. protective mechanism is the identifjcation of INTRODUCTION the specifjc neurovascular space where the infection resides, be it the meninges, the epidural Infections of the central nervous system (CNS) space, or the parenchyma itself. The extent of are varied in their causes, presentations, and the neurovascular space involved in infections is prognosis. They can be sudden in onset and often a spectrum extending from the meninges have the potential to cause signifjcant morbidity to the encephalon. An infectious agent that and mortality. A particular clinical challenge for initially causes meningitis can easily progress to CNS infections is the relatively isolated nature encephalitis, also known as meningoencephalitis. of the CNS and its protective mechanisms. The The extent of disease produced by a specifjc blood–brain barrier is the main protective feature agent can also vary drastically between patients. of the CNS and works to restrict the passage of pathogens and large molecules from the This article is a review on the initial approach to bloodstream into the cerebrospinal fmuid (CSF). a patient with suspected neurological infection It is composed of a network of specialised with emphasis on clinical presentation, diagnosis, brain endothelial cells as well as pericytes and and treatment of meningitis and encephalitis. astrocytes that support brain capillaries. 1,2 A specifjc challenge that arises as a result of this 93 Creative Commons Attribution-Non Commercial 4.0 July 2020 • NEUROLOGY

main examples of neurotropic viruses that can MENINGITIS frequently cause disease. HSV-1 infection can cause severe encephalitis in adults whereas in children, The meninges are a triple-layer membranous HSV-2 tends to cause more serious infections. envelope composed of the pia mater, dura However, incidental and non-neurotropic viruses mater, and arachnoid space. Meningitis refers account for the majority of viral meningitis cases. to infmammation of the leptomeninges and Nonpolio enteroviruses account for more than CSF within the subarachnoid space that exists 85% of all cases of viral meningitis. 9 between the pia mater and the arachnoid layers. 3 The exact cause of the infmammation, however, Clinical Presentation can vary. There is a myriad of infectious and Meningitis must be considered in any patient noninfectious causes of meningitis, but for the presenting with fever and headache. Diagnosis purpose of this review, the focus will be acute infections of the meninges. Primary infectious is complicated by the fact that the full triad of fever, nuchal rigidity, and meningismus is causes include bacterial, viral, and fungal origins. rarely present. A thorough history and physical Meningitis secondary to a bacterial infection exam to rule out other common aetiologies can cause signifjcant morbidity and mortality is paramount. Establishing pretest probability as a result of the severe infmammation. The is important because the gold standard to infmammation can cause signifjcant oedema of the diagnose meningitis, lumbar puncture (LP), and surrounding structures and increased intracranial CSF culture, is an invasive and skilful procedure pressure. 4 Many organisms, such as Escherichia that can be diffjcult to perform under certain coli and Neisseria meningitidis , are pyogenic and circumstances. Common historical features can cause a thick suppurative exudate that covers of patients with meningitis include headache, the brainstem and thickens the leptomeninges. 3 vomiting, and neck pain. 10 The presence of The main pathogenic bacteria implicated these symptoms alone has poor sensitivity, with in meningitis varies by age and degree of the pooled sensitivity for headache being 50% immunocompromise. The most common causes (95% confjdence interval: 32–68%) and 30% of meningitis in neonates are Streptococcus for nausea/vomiting (95% confjdence interval: agalactiae and E. coli . Whereas in children beyond 22–38%). 10 However, the absence of fever, neck the neonatal period, the most common agents are stifgness, and altered mental status efgectively N. meningitidis and Streptococcus pneumoniae . 5 eliminates meningitis. 10 As far as physical signs Common agents in adults include N. meningitidis are concerned, Kernig’s and Brudzinski’s signs and S. pneumoniae , but Listeria monocytogenes were both described in the late 1800s and early must also be considered, particularly in the elderly. 1900s, respectively. Most of the patients they studied had signifjcant meningeal infmammation Another important pathogen to consider is with underlying Mycobacterium tuberculosis and Haemophilus infmuenzae type b (Hib). Widespread S. pneumoniae infections. 11 Multiple recent studies vaccination has signifjcantly decreased the have shown poor sensitivity of these signs, even incidence of Hib meningitis by over 90% in some in the presence of jolt accentuation. 12,13 Despite countries. 6,7 However, it remains a prevalent poor sensitivity, these signs are quite specifjc (92– pathogen in underdeveloped and unvaccinated 95%) for pleocytosis, which again demonstrates populations. Hib can cause severe bacterial the importance of a detailed exam. Overall, meningitis in children with signifjcant morbidity. Up clinical gestalt is the best guiding feature in to 20% of children that recover from Hib meningitis pursuing a workup of meningitis and establishing experience long-term neurological sequelae such the diagnosis. as sensorineural hearing loss, developmental Diagnosis delay, seizures, and hydrocephalus. 8 Hib can also cause signifjcant disease in immunocompromised The hallmark diagnostic procedure for meningitis and asplenic patients at any age. is LP. Serum laboratory markers can indicate Viral meningitis is usually less clinically severe overall presence of infmammation, but none can than bacterial meningitis. Herpes simplex virus specifjcally diagnose meningitis. The specifjc (HSV) and varicella-zoster virus (VZV) are two technique and contraindications of the procedure 94 EMJ NEUROLOGY • July 2020