Neuroimaging plays a crucial role in the diagnosis in infectious diseases of the central nervous system. The review summarizes top 10 important things to know in the imaging diagnosis of infectious diseases of the central nervous system. 1. Herpes simplex virus encephalitis. MR image shows high signal in the temporal lobes, insulae, and cingulate gyri bilaterally on T2-weighted images, FLAIR images and diffuse weighted images. 2. Varicella-zoster virus (VZV)infection. MR images shows multiple focal high signal intensities in cerebral cortices and white matters especially peri-ventricular areas on T2-weighted images. VZV vasculopathy causes cerebral arteries occlusion resulting in cerebral infarctions and rarely hemorrhages. 3. Japanese encephalitis. Bilateral thalamic and nigral involvement is classical MR imaging. Other areas may be involved are pons, cerebellum, basal ganglia, cerebral cortex and spinal cord. 4. Influenza encephalopathy includes acute necrotizing encephalopathy, acute brain swelling encephalopathy, hemorrhagic shock and encephalopathy syndrome (HSES), Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD), mild encephalitis/encephalopathy with a reversible splenial lesion (MERS). 5. progressive multifocal leukoencephalopathy (PML)shows asymmetric periventricular and subcortical white matters, brainstem and cerebellar white matters involvement. Lesions show T1 and T2 prolongation and sometimes diffusion restriction. 6. human immunodeficiency virus encephalopathy/encephalitis shows symmetric cerebral white matter T2 prolongation. 7. Cerebral abscess and subdural empyema shows diffusion restriction on diffusion weighted images and are critical for the diagnosis. Bacterial meningitis shows meningeal enhancement on post gadolinium T1-weighted images. 8. The neuroimaging characteristics of tuberculous meningitis classically include leptomeningeal and basal cisternal enhancement, ventriculomegaly due to hydrocephalus, periventricular infarcts, and the presence of tuberculomas. 9. Neurosyphilis shows cerebral and meningovascular involvement and appears T2 prolongation and meningeal contrast enhancement. Syphilitic gummas appear as small focal nodules adjacent to the meninges and shows homogeneous contrast-enhancement. 10. cerebral sparganosis mansoni typically shows tubular enhancement in a linear or curvilinear fashion-the tunnel sign-on post gadolinium T1-weighted images

A 44-year-old man developed headache, slight fever, and memory disturbance eight months ago, and he was admitted to our hospital due to abnormal behavior and disturbed consciousness. Meningitis was suspected because of disturbed consciousness and neck stiffness. Considering his immunocompromised backgrounds, long-lasting symptoms, imaging findings, and cerebrospinal fluid (CSF) findings, tuberculous meningitis was the most probable diagnosis. Nevertheless, we failed to detect the pathogen by culture test, nested PCR, cytodiagnosis, and meninges and brain biopsy. Administration of antituberculosis drugs successfully reduced the patient's CSF cell count but his symptoms remained unchanged. On the other hand, the symptoms gradually improved by VP shunt for secondary hydrocephalus. Here we present this unusual case of meningitis and discuss the difficulties in making a definite diagnosis of tuberculous meningitis and those in assessing the efficacy of antituberculosis treatment under the presence of secondary hydrocephalus.

Background : While Human T-cell leukemia virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a slowly progressive neurological disease, the progression of the disease varies from person to person. While some blood or cerebrospinal fluid biomarkers for rapid progression of HAM/TSP have been reported, no clinical parameter associated with rapid progression of HAM/TSP has been identified except for older age. Purpose : We tried to find the initial symptom associated with rapid progression of the disease using registry data on patients ( n=527 ) enrolled in the Japanese HAM/TSP patient registry "HAM-net." We determined the periods from the onset of HAM/TSP to the age of wheelchair use in daily life of all the patients and compared the periods by their initial symptom. Result : Urinary disturbance as an initial symptom was significantly associated with slowly progression of HAM/TSP. Sensory disturbance as an initial symptom was significantly associated with rapid progression. Conclusion : The result showed that Initial symptoms could suggest the disease course of the patients with HAM/TSP.

We experienced a case of meningitis caused by Rat-bite fever, Streptobacillus notomytis. Because of the S. notomytis specific gene detected from cerebrospinal fluid and the polymorphism-negative bacilli found in equine blood medium carbon dioxide culture, we could diagnose the meningitis caused by S. notomytis. We administered ampicillin which was reported to be effective against rat-bite fever in addition to meropenem for the 1st hospital day. As a result, the patient recovered from Rat-bite fever. Compared with the Rat-bite fever caused by S moniliformis, this case is characterized by the absence of preceding septicemia, no rash, and a long incubation period. It was difficult to diagnose without taking detailed medical history.