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The constellation of fever, generalized weakness, and bulbar dysfunction can be from a multitude of diseases. Grouping them according to location of disease is useful in guiding diagnostic tests that are needed. Infectious etiologies for central nervous system (CNS) dysfunction (ie, meningitis, encephalitis, cerebral abscess) are important to diagnose and treat quickly. Given the emergent necessity of treating infectious etiologies of meningitis and/or encephalitis, it is prudent to begin treatment with antiviral and antibacterial agents while diagnostic testing proceeds. Intravenous acyclovir should be strongly considered as well as intravenous medication to treat bacterial meningitis, tuberculosis, and fungal infections, depending on clinical suspicion. Diagnosis and treatment of infectious diseases will be discussed in Chapter 7. To diagnose CNS infection, a lumbar puncture should not be delayed.
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Although unlikely in this case, perhaps the most time-sensitive diagnosis would be a vascular etiology. In a patient with vascular risk factors and cranial nerve signs/symptoms, a posterior circulation ischemic event is most important to diagnose quickly. Although a noncontrast head CT is effective in diagnosing intracerebral hemorrhages, in this setting it is probably not very helpful. Magnetic resonance imaging (MRI) of the brain is the most effective tool for diagnosing ischemic strokes and also will help in diagnosing other diseases.
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Once infectious and vascular etiologies are addressed, one must consider inflammatory diseases. The history of symptoms occurring after a viral prodrome, malaise, and low-grade fever is suggestive of a postinfectious inflammatory process. Acute disseminated encephalomyelitis (ADEM) is a disease that can cause rapid mental status changes and multifocal neurologic deficits. An MRI with and without gadolinium is necessary to diagnose ADEM.
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Other possible parenchymal diseases include metastatic disease, other autoimmune inflammatory diseases such as tumefactive multiple sclerosis (MS), and CNS manifestations of systemic autoimmune diseases: lupus, Behçet syndrome, vasculitis, and paraneoplastic diseases.
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Leptomeningeal processes can cause encephalopathy and multifocal neurologic symptoms. Again, infectious processes are the most urgent to diagnose. Other possibilities are inflammatory diseases such as sarcoid, neoplastisms, and carcinomatous meningitis.
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Although the patient's encephalopathy suggests otherwise, another important location of disease can be in the peripheral nervous system. Demyelinating diseases such as Guillain-Barré syndrome (GBS) can progress over days and impair bulbar function. In fact, some diseases can affect both the central and peripheral nervous systems to produce this clinical syndrome. Bickerstaff encephalitis, a variant of GBS, involves ophthalmoplegia, ataxia, and encephalopathy. It is associated with peripheral motor axonal demyelination with brainstem encephalitis. The detection of the antiganglioside immunoglobulin G (IgG) GQ1b antibody is helpful in the diagnosis of this disease.1 In a recent case series of patients with ADEM, 43% had polyradiculoneuropathy; mostly demyelinating.2 If there is clinical suspicion for peripheral involvement, electromyography and nerve conduction studies (EMG/NCSs) are warranted. Patterns seen on EMG/NCS are discussed in Chapter 6.
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The patient underwent a lumbar puncture that showed: 10 white blood cells (WBCs); 67% lymphocytes; 33% monophils; 0 red blood cells (RBCs); glucose 65; protein 80; albumin index 11.4 (elevated); herpes simplex virus polymerase chain reaction (HSV PCR) negative; no detected oligoclonal bands; bacterial cultures negative; encephalitis panel negative; paraneoplastic panel negative.