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1、Viral meningitis refers to meningitis caused by a viral infection. Children and young adults are frequently affected. Viral meningitis is most often caused by enteric 肠道的viruses Viral encephalitis by childhood exanthems皮疹, arthropod-borne节肢动物agents虫媒性病原体, and herpes simplex type 1.,Cause,最常见 柯萨奇病毒 E
2、CHO病毒 肠道病毒,其次 流行性腮腺炎 单纯疱疹病毒 腺病毒,Pathology,Viral infections can affect the central nervous system in three ways 血源性播散 ：hematogenous dissemination of a systemic viral infection(eg, arthropod-borne viruses虫媒性病毒); 轴突传播：neuronal spread of the virus by axonal transport (eg, herpes simplex, rabies狂犬病病毒); 自
3、身免疫性感染后脱髓鞘：autoimmune postinfections demyelination脱髓鞘 (eg, varicella水痘病毒, influenza).,Pathologic changes in viral meningitis consist of an inflammatory meningeal reaction mediated by lymphocytes.,病毒性脑膜炎的病理改变是由淋巴细胞介导的炎性脑膜反应。,Encephalitis is characterized by perivascular cuffing, lymphocytic infiltrat
4、ion, and microglial proliferation mainly involving subcortical gray matter regions. Internuclear or intracytoplasmic inclusions are often seen. 病毒性脑炎的病理改变特点是血管周围套袖样改变、淋巴细胞浸润，以及累及皮层下灰质的小胶质增生，并经常可见到核浆或细胞浆内包涵体。,Clinical findings-symptoms and signs,Clinical manifestations include fever, headache, neck s
5、tiffness, photophobia畏光, pain with eye movement, and mild impairment of consciousness. Patients usually do not appear as ill as those with bacterial meningitis. Systemic viral infection may cause skin rash, pharyngitis咽炎, lymphadenopathy淋巴结病, pleuritis胸膜炎, carditis心肌炎, jaundice黄疸, organomegaly器官肿大,
6、diarrhea腹泻, or orchitis睾丸炎, and these findings may suggest a particular etiologic agent病原体.,Because viral encephalitis involves the brain directly, marked alterations of consciousness, seizures, and focal neurologic signs can occur. When signs of meningeal irritation脑膜刺激征and brain dysfunction coexis
7、t共存, the condition is termed meningoencephalitis脑膜脑炎.,Laboratory findings,CSF analysis is the most important laboratory test. CSF pressure is normal or increased a lymphocytic or monocytic pleocytosis脑脊液细胞数增多 is present, with cell counts usually less than 1000/ml. (higher counts can be seen in lymph
8、ocytic choriomeningitis脉络丛脑膜炎or herpes simplex encephalitis.) A polymorphonuclear多形核白细胞 pleocytosis can occur early in viral meningitis, while red blood cells may be seen with herpes simplex encephalitis.,Protein is normal or slightly increased (usually 80120mg/dL). Glucose is usually normal, but ma
9、y be decreased in mumps腮腺炎, herpes zoster带状疱疹, or herpes simplex encephalitis. Grams stain and bacterial, fungal, and acid-fast bacillius(AFB) cultures are negative. Oligoclonal bands寡克隆区带and CSF protein electrophoresis电泳abnormalities may be present. An etiologic diagnosis can often be made by virus
10、 isolation, polymerase chain reaction, or acute- and convalescent phase恢复期CSF antibody titers抗体滴度.,Blood counts may show a normal white cell count, leukopenia白血球减少症, or mild leukocytosis白细胞增多. Serum amylase血清淀粉酶is frequently elevated in mumps 腮腺炎; abnormal liver function tests are associated with bo
11、th hepatitis viruses肝炎病毒and infectious mononucleosis单核细胞增多症.,The EEG is diffusely slow, especially if there is direct cerebral involvement.,Diagnosis,Differential diagnosis,The differential diagnosis of meningitis with mononuclear cell pleocytosis includes partially treated bacterial meningitis治疗不彻底
12、的细菌性脑膜炎 as well as syphilitic梅毒的, tuberculous结核性的, fungal, parasitic寄生物的, neoplastic肿瘤的, and other meningitides脑(脊)膜炎.,Evidence of systemic viral infection and CSF wet mounts, stained smears, cultures, and cytologic examination细胞学检查can distinguish among these possibilities. When presumed early viral
13、 meningitis is associated with a polymorphonuclear多形核白细胞pleocytosis of less than 1000 white blood cells/mL and normal CSF glucose, one of two strategies can be used.,The paitent can be treated for bacterial meningitis until the results of CSF cultures are known; Treatment can be withheld and lumbar
14、puncture腰椎穿刺术 repeated in 612 hours. If the meningitis is viral in origin, the second sample should show a mononuclear cell pleocytosis.,A disorder that may be clinically indistinguishable from viral encephalitis is the immune-mediated encephalomyelitis that may follow viral infections such as influ
15、enza, measles麻疹, or chickenpox水痘. Progressive neurologic disfunction typically begins a few days after the viral illness, but can also occur either simultaneously同时发生 or up to several weeks later.,Neurologic abnormalities result from perivenous 静脉周围的demyelination脱髓鞘, with often severely affects the
16、brainstem. The CSF shows a lymphocytic pleocytosis脑脊液细胞数增多, usually with cell counts of 50150/mL, and mild protein elevation.,Treatment,Except for herpes simplex encephalitis, which is discussed separately no specific therapy for viral meningitis and encephalitis is available. Corticosteroids are of
17、 no proven benefit except in immune-mediated postinfectious syndromes.,Headache and fever can be treated with acetaminophen醋氨酚, but aspirin should be avoided, especially in children and young adults, because of its association with Reyes syndrome. Seizures usually respond to phenytoin 苯妥英钠or phenoba
18、rbital苯巴比妥. Supportive measures in comatose昏睡的patients include mechanical ventilation and intravenous or nasogastric feeding鼻饲.,Prognosis,Symptoms of viral meningitis usually resolve spontaneously within 2 weeks regardless of the causative agent, although residual deficits后遗症may be seen. The outcome
19、 of viral encephalitis varies with the specific virus -for example, herpes simplex virus infections are associated with severe morbidity and high mortality rates. Mortality rates as high as 20% have also been reported in immune-mediated encephalomyelitis脑脊髓炎following measles麻疹 infections.,Herpes sim
20、plex virus (HSV) encephalitis,HSV is the most common cause of sporadic散发的 fatal encephalitis in the United States. About two-thirds of cases patients over 40 years of age. Primary herpes infections most often present as stomatitis口炎( HSV type 1) or a venereally 性交的transmitted genital生殖器eruption出疹 (H
21、SV tpye 2).,The virus migrates along nerve axons轴突to sensory ganglia神经节, where it persists in a latent form and may be subsequently reactivated. It is not clear whether HSV type 1 encephalitis, the most common type in adults, represents a primary infection or a reactivation of latent infection.,Neon
22、atal新生儿的HSV encephaltis usually results from acquisition获得of type 2 virus during passage through the brith canal of a mother with active genital生殖器的lesions. Central nervous system involvement by HSV type 2 in adults usually causes meningitis, rather than encephalitis.,Pathology,HSV tpye 1 encephalit
23、is is an acute, necrotizing引坏死的, asymmetric不对称的hemorrhagic出血性的process with lymphocytic and plasma cell浆细胞reaction. Usually involves the medial temporal and inferior frontal lobes. Intranuclear inclusions核内包涵体may be seen in neurons神经元and glia神经胶质. Patients who recover康复期 may show cystic囊的necrosis坏死of
24、 the involved regions.,嗜酸性Cowdry A型包涵体,Clinical Finding- A Symptoms and Signs,The clinical syndrome may include headache, stiff neck, vomiting, behavioral disorders, memory loss, anosmia嗅觉丧失, aphasia, hemiparesis轻偏瘫, and focal or generalized seizures.,Active herpes labialis唇疱疹is seen occasionally, b
25、ut does not reliably implicate HSV as the cause of encephalitis.,HSV encephalitis is uaually rapidly progressive over several days and may result in coma or death. The most common sequelae 后遗症 in patients who survive are memory and behavior disturbances, reflecting the predilection 嗜好, 偏爱of HSV for
26、limbic structures.,Laboratory Findings,Laboratory Findings-CSF,The CSF in HSV tpye 1 encephalitis most often shows increased pressure lymphocytic or mixed lymphocytic and polymorphonuclear多形核白细胞 pleocytosis( 50100 white blood cells/mL) mild protein elevation, and normal glucose. Red blood cells, xan
27、thochromia 黄变, and decreased glucose are seen in some cases.,Laboratory Findings-VIRUS,The virus generally cannot be isolated from the CSF, but viral DNA has been detected by the polymerase chain reaction聚合酶链反应in some cases.,HSV抗体检定,ELASA是现今国际上通用的HSV抗体检测方法。 本方法采用双份血清和双份脑脊液作HSV-1抗体的动态检测。 诊断标准： 双份CSF抗
28、体有增高趋势，滴度1:8以上； 双份CSF抗体4倍以上升高； 血与CSF的抗体比值40。,Laboratory Findings-EEG,The EEG may show periodic周期的slow-wave complexes arising from one or both temporal lobes,Laboratory Findings- CT MRI,CT scans and MRI may show abnormalities in one or both temporal lobes. These can extend to frontal or parietal regi
29、ons顶区and are sometimes enhanced with the infusion注入of contrast material造影剂. However, imaging studies may also be normal.,Diagnosis,Differential Diagnosis,The symptoms and signs are not specific for herpes virus infection. The greatest diagnostic difficulty is distinguishing between HSV encephalitis
30、and brain abscess脑脓肿, and the tow disorders often cannot be differentiated on clinical grounds alone.,brain abscess,brain abscess,Other CNS infections and vasculitis血管炎can also mimic HSV encephalitis. Deginitive diagnosis can be made by biopsy of affected brain areas, with the choice of biopsy site
31、guided by the EEG, CT, or MRI findings. However, because treatment is most effective when begun early and is comparatively safe, the most common approach is to treat patients with possible HSV encephalitis as described below and to reserve biopsy for those who fail to improve.,Treatment,The most eff
32、ective drug is acyclovir阿昔洛韦 Given intravenously at a dosage of 1015mg/kg every 8 hours, with each dose given over 1 hour. Treatment is continued for 1421 days.,Complications include erythema红斑at the infusion site, gastrointestinal 胃肠道disturbances, headache, skin rash, tremor, seizures, and encephal
33、opathy脑病or coma. Treatment is started as early as possible, since outcome is greatly influenced by the severity of dysfunction at the time treatment is initiated.,肾上腺皮质激素,地塞米松 甲泼尼龙,Prognosis,Patients under the age of 30 years and those who are only lethargic昏睡的at the onset of treatment are more likely to survive than are older or comatose patients. The mortality rate is about 25% at 18 months in patients given acyclovir阿昔洛韦.,