**2. CSF findings in viral encephalitis**

Cerebrospinal fluid (CSF) is produced in choroid plexus of brain ventricules and in subar‐ achnoid pial surface. Noninfective CSF contains maximum 5 wight blood cells (WBC) in a mm3 . The protein content in normal CSF does not exceed 50mg/dl and CSF glucose is 50-70 % of serum glucose levels. Central nervous system infections alter this normal content in varied degrees. Thus, knowing these alerations in various infectious and noninfectious sit‐ uations is crucial for attaining veritable diagnosis. CNS infections should be born in mind in patients, who attain to emergency departments with fever, impaired consciousness and findings attributed to nervous system. Obtaining CSF with lumber puncture performed in early period leads to at once, differentiation of central pathologies from systemic ones, of in‐ fectious etiologies from noninfectious causes, and getting data concerning the character of a possible central nervous system infection; therefore CSF analysis maintains its importance as a valid method currently, for searching brain infections.

Lumbar puncture is performed generally from L4-5 intervertebral space. However L3-4 and L5-S1 intervertebral spaces are also utilized. Sufficient CSF sample should be obtained for routine laboratory tests, and a certain amount should be spared for advanced tests. Initially, protein and glucose levels are analysed from obtained sample, white blood cell count is done, and cultural analyses are performed. Opening pressure and protein concentration are increased, and glucose levels are decreased in bacterial menengitis. Polymorphonuclear cells (PNL) are usually found. Opening pressure is normal or mildly increased however in viral encephalitis and menengitis. In a classical viral encephalitis glucose levels are normal, but protein concentration is found to be mildly or moderatly increased. CSF findings in several infectious situations is summarized in Table 3.


**Table 3.** General characteristics of various CNS infections

Clinical findings (physical and specific neurological signs and symptoms) may indicate cer‐ tain causative agents in patients with encephalitis (Table 2). This table is again revisely taken

from the same guideline mentioned in the previous paragraph [1];

Lymphadenopathy HIV, EBV, CMV, Measles virus, Rubella virus, West Nile virus,

Enteroviruses,

Adenovirus,

CMV, West Nile virus,

Cerebellar ataxia VZV (in children), EPV, Mumps virus, St. Louis encephalitis virus,

panencephalitis (SSPE))

virus,

Rhombencephalitis HSV, West Nile virus, Enterovirus 71

**2. CSF findings in viral encephalitis**

**Table 2.** Possible etiological agents of viral Encephalitis based on clinical findings

Rash VZV, B virus, Human herpesvirus 6, West Nile virus, Rubella virus, certain

St Louis encephalitis virus (early)

Dementia HIV, Human transmissible spongiform encephalopathies, sCJD and variant

Parkinsonism Japanese encephalitis virus, St. Louis encephalitis virus, West Nile virus, Nipah

Cerebrospinal fluid (CSF) is produced in choroid plexus of brain ventricules and in subar‐ achnoid pial surface. Noninfective CSF contains maximum 5 wight blood cells (WBC) in a

. The protein content in normal CSF does not exceed 50mg/dl and CSF glucose is 50-70 % of serum glucose levels. Central nervous system infections alter this normal content in varied degrees. Thus, knowing these alerations in various infectious and noninfectious sit‐ uations is crucial for attaining veritable diagnosis. CNS infections should be born in mind in patients, who attain to emergency departments with fever, impaired consciousness and findings attributed to nervous system. Obtaining CSF with lumber puncture performed in

Poliomyelitis-like flaccid paralysis Japanese encephalitis virus, West Nile virus, Tick-born encephalitis virus,

Creutzfeldt-Jacob disease (vCJD), Measles virus (Subacute sclerosing

Enterovirus (enterovirus-71, coxsackieviruses), Poliovirus

Respiratory tract findings Venezuela equine encephalitis virus, Nipah virus, Hendra virus, Influenza virus,

**Clinical presentation Possible infectious agent**

Parotitis Mumps virus

Cranial nerve abnormalities HSV, EBV,

General findings

24 Encephalitis

Retinitis

mm3

Urinary symptoms

Neurological findings

In viral encephalitis, a more important problem is to find out the etiological agent and to apply therefore the appropriate antiviral agent beginning from the early period of the disease. Nevertheless, CSF findings, as they are analysed by routine tests, are not specific in viral encephalitis, and couldn't be heplfull to distinguish different etiological agents. These findings combined with radiological data could also not be assistant, and determi‐ nation of etiology may be delayed. As a matter of fact, various serological methods, cell cultures and genom analyses are widely utilised currently. Methods to apply should be adapted to geographical factors, to epidemyological data, and to travel history in a spe‐ cific individual. Negative results does not always rule out a certain agent, therefore re‐ peated tests could be needed.

A hemorhagic CSF could be seen in Herpes simplex type I encephalitis [5]. Lymphositic pleocytosis (10-500 mononuclear cell/mm3 ) and increased protein concentrations are usually found [6]. However, in immuncompromised patients especially, one could not encounter typical pleocytosis. Thus, CSF findings could be misleading in such situations; before ruling out the disease or an etiological agent, a wider CSF screen is needed in these patients. Deter‐ mination of HSV-DNA with polymerase chain reaction (PCR) is a widely utilised method today. As a gold diagnostic standart currently, PCR's sensitivity is 95 % in Herpes simplex type I, and its specifity is 100 % [7]. Since the identification of HSV-I in the early period of the disease is an ongoing problem, the test should be repeated after 3-7 days in cases with negative results [1]. Studies searching for the association between HSV-DNA load and dis‐ ease prognosis haven't revealed consistent results hitherto; hence, further studies are need‐ ed [8]. Isolation of the virus in cell culture is also possible, but methods sensitivity is quite low and is not invoked in clinical practice widely. Another method is to determine specific antibodies. Blood/CSF antibody ratio below 20/1 exposes the intratecal synthesis and is use‐ full in diagnosis of Herpes simplex encephalitis in a considerable degree. Positive PCR re‐ sults are tend to diminish with the parenteral application of acyclovir, possibility of a positive test after second week is quite decreased; in contrast, in this period of the disease, specific antibodies are easily determined. The fact that patients with negative PCR and posi‐ tive oligoclonal bands are frequently encountered in a specific period of the disease suggests that these two methods are sensitive to different stages of the diseases [9]. Recent studies displayed some inflamatory cytokine level alterations in CSF. While in the early period of the disease the IFN-γ and IL-6 levels are high, at the period of 2-6 weeks, TNF-α, IL-2 and soluable CD8 levels are found to be increased [10]. Maybe, these findings are reflecting the neuronal damage and inflamatory reaction, however the clinical importance of them are not well established currently.

cific antibodies may express cross-reaction with Parainfluenza virus antibodies [6]. In the course of encephalitis caused by Enteroviruses, CSF cell count is generally normal, or a mildly mononuclear pleocytosis is present. Glucose levels are normal and protein concentra‐ tion is increased. Method to be choosen is RT-PCR. Sensitivity and specifity are 86 % and 100 % respectively. Cell culture may also be helpfull. Despite Influenza encephalitis is rarely reported, it should be investigated in pandemic situations and/or in conditions, in which no other etiological agent is determined. Routine CSF screen is usually normal. The etiological

> **BACTERIAL FUNGAL MENENGITIS**

**LCMV MUMPS HERPES/VZV (rare) ENCEPHALITIS**

In encephalitis caused by Flaviviruses, clinical suspicion maintains its importance. Methods that target Flaviviruses should be added to routine CSF analyses in endemic regions, or in patients who have a travel history; at times, repeated lumbar punctures are needed for de‐ termining the etiological agent. In West nile virus encephalitis, domination of polymorpho‐ nuclear leukocytes in hyperacute period, leaves its place to lympocytes afterwards. CSF

**TBC MENENGIT IS**

Cerebrospinal Fluid Abnormalities in Viral Encephalitis

http://dx.doi.org/10.5772/54590

27

analysis is performed by RT-PCR and cell culture in suspected cases.

HSV-1 PCR, quantitative PCR, routine serology

HSV-2 PCR, routine serology, culture

HHV-6, HHV-7 PCR, routine serology, culture VZV PCR, routine serology, VZV Ge

**Table 4.** Diagnostic methods in herpesviridae family.

**Figure 1.** CNS infections, in which low CSF glucose levels are found.

EBV PCR, routine serology

CMV PCR

**LOW CSF GLUCOSE**

A lymphocytic pleocytosis is seen in Varicella zoster virus (VZV) encephalitis (below 100 cells/mm3 ), and increased protein concentrations and normal glucose levels are found. Opening pressure maybe increased [6]. In cell culture, the virus is rarely isolated. VZV-PCR is a usefull technique for determining the agent. Once again, negative results do not rule out the virus. In many cases, virus DNA is diminished in CSF after the first week, hence the way to be chosen is to analyze intrathecal antibodies at this period. Determining the ratio of IgG antibodies to blood content or IgM levels are helpfull. VZV glycoprotein E does not express antigenic resemblance with the herpes simplex virus, and is easily determined with per‐ forming ELISA. This method has a high specifity and sensitivity for VZV encephalitis, it may also be utilised for the differential diagnosis with herpes virus [11]. The test to be choosen in Ebstein-Barr virus and in Citomegalovirus encephalitis is again PCR. Negative results do not exclude the agents. Determining the alterations of IgM and IgG levels with serological analyses maybe usefull in EBV encephalitis. HHV-6 and HHV-7 PCR tests should be added to routine CSF screen in immuncompromised patients [5]. It should also be noted that HHV-6 PCR does not distinguish latent infection from active encephalitis. Diag‐ nostic methods for encephalitis caused by herpesviridea family is shown in Table 4.

Besides HSV and VZV, PCR test is trusty also in JC virus. In immuncompromised patients in whom multifocal leucoencephalopathy is suspected, PCR technique is highly specific. Pleocytosis is charactheristic in Mumps encephalitis. Interestingly however, protein levels are generally normal and glucose concentrations are decreased. The disease should be dif‐ ferentiated from Lymphocytic choriomenengit virus, since decreased glucose levels are re‐ sulted also from that agent caused encephalitis (Figure 1). Cell culture and PCR are equally helpfull. Specific antibodies should be investigated if PCR is negative. Four fold increase in IgG levels or determining IgM are helpfull, but it should be born in mind that Mumps spe‐ cific antibodies may express cross-reaction with Parainfluenza virus antibodies [6]. In the course of encephalitis caused by Enteroviruses, CSF cell count is generally normal, or a mildly mononuclear pleocytosis is present. Glucose levels are normal and protein concentra‐ tion is increased. Method to be choosen is RT-PCR. Sensitivity and specifity are 86 % and 100 % respectively. Cell culture may also be helpfull. Despite Influenza encephalitis is rarely reported, it should be investigated in pandemic situations and/or in conditions, in which no other etiological agent is determined. Routine CSF screen is usually normal. The etiological analysis is performed by RT-PCR and cell culture in suspected cases.


**Table 4.** Diagnostic methods in herpesviridae family.

type I, and its specifity is 100 % [7]. Since the identification of HSV-I in the early period of the disease is an ongoing problem, the test should be repeated after 3-7 days in cases with negative results [1]. Studies searching for the association between HSV-DNA load and dis‐ ease prognosis haven't revealed consistent results hitherto; hence, further studies are need‐ ed [8]. Isolation of the virus in cell culture is also possible, but methods sensitivity is quite low and is not invoked in clinical practice widely. Another method is to determine specific antibodies. Blood/CSF antibody ratio below 20/1 exposes the intratecal synthesis and is use‐ full in diagnosis of Herpes simplex encephalitis in a considerable degree. Positive PCR re‐ sults are tend to diminish with the parenteral application of acyclovir, possibility of a positive test after second week is quite decreased; in contrast, in this period of the disease, specific antibodies are easily determined. The fact that patients with negative PCR and posi‐ tive oligoclonal bands are frequently encountered in a specific period of the disease suggests that these two methods are sensitive to different stages of the diseases [9]. Recent studies displayed some inflamatory cytokine level alterations in CSF. While in the early period of the disease the IFN-γ and IL-6 levels are high, at the period of 2-6 weeks, TNF-α, IL-2 and soluable CD8 levels are found to be increased [10]. Maybe, these findings are reflecting the neuronal damage and inflamatory reaction, however the clinical importance of them are not

A lymphocytic pleocytosis is seen in Varicella zoster virus (VZV) encephalitis (below 100

Opening pressure maybe increased [6]. In cell culture, the virus is rarely isolated. VZV-PCR is a usefull technique for determining the agent. Once again, negative results do not rule out the virus. In many cases, virus DNA is diminished in CSF after the first week, hence the way to be chosen is to analyze intrathecal antibodies at this period. Determining the ratio of IgG antibodies to blood content or IgM levels are helpfull. VZV glycoprotein E does not express antigenic resemblance with the herpes simplex virus, and is easily determined with per‐ forming ELISA. This method has a high specifity and sensitivity for VZV encephalitis, it may also be utilised for the differential diagnosis with herpes virus [11]. The test to be choosen in Ebstein-Barr virus and in Citomegalovirus encephalitis is again PCR. Negative results do not exclude the agents. Determining the alterations of IgM and IgG levels with serological analyses maybe usefull in EBV encephalitis. HHV-6 and HHV-7 PCR tests should be added to routine CSF screen in immuncompromised patients [5]. It should also be noted that HHV-6 PCR does not distinguish latent infection from active encephalitis. Diag‐

nostic methods for encephalitis caused by herpesviridea family is shown in Table 4.

Besides HSV and VZV, PCR test is trusty also in JC virus. In immuncompromised patients in whom multifocal leucoencephalopathy is suspected, PCR technique is highly specific. Pleocytosis is charactheristic in Mumps encephalitis. Interestingly however, protein levels are generally normal and glucose concentrations are decreased. The disease should be dif‐ ferentiated from Lymphocytic choriomenengit virus, since decreased glucose levels are re‐ sulted also from that agent caused encephalitis (Figure 1). Cell culture and PCR are equally helpfull. Specific antibodies should be investigated if PCR is negative. Four fold increase in IgG levels or determining IgM are helpfull, but it should be born in mind that Mumps spe‐

), and increased protein concentrations and normal glucose levels are found.

well established currently.

cells/mm3

26 Encephalitis

**Figure 1.** CNS infections, in which low CSF glucose levels are found.

In encephalitis caused by Flaviviruses, clinical suspicion maintains its importance. Methods that target Flaviviruses should be added to routine CSF analyses in endemic regions, or in patients who have a travel history; at times, repeated lumbar punctures are needed for de‐ termining the etiological agent. In West nile virus encephalitis, domination of polymorpho‐ nuclear leukocytes in hyperacute period, leaves its place to lympocytes afterwards. CSF protein concentrations are usually increased, glucose levels are normal. RT-PCR is assistant, but it is not possible in late stages of the disease to capture the virus RNA [12]. Virus isola‐ tion by means of CSF cultures is also utilised [13]. Today the most valid methods are sero‐ logical approaches. The success of ELISA in detecting WNV-specific antibodies is increased in 8-21 days after the beginning of clinical symptoms. Similar serological methods can be used in other Flavivirus infections. In Japan encephalitis, for example, the valid method cur‐ rently is ELISA capture of JE-IgM [14] (Table 5). Various biomarkers, which are detected in CSF in the course of WNV encephalitis may reflect the severity of disease and neuronal damage. In 58 % of cases with WNV, NfH-SM135 and GFAP-SM126 can be found positive, S100B positivity is seen in 90 % of this same group [15]. In Eastern equine encephalitis, leu‐ cocyte count is much more increased, and it can reach 1000-2000 cells per mm3 ; it should al‐ so be noted that dominant cells are polymorphnuclear. CSF findings emerged from various encephalitic situations are summarized in Table 6.

CSF findings in all types of encephalitis may expose time dependent alterations. In cases with negative PCR, repeated lumbar punctures should be performed, differences in cell count should be observed, PCR studies should be repeated and new cell cultures should be made for virus isolation. This aproach is valid in patients receiving amprical antiviral treat‐ ment also. For example, it is known that PCR becomes positive several days after the onset of clinical symptoms in herpes encephalitis. PCR test becomes negative after a certain time in HSV and VZV encephalitis. This duration is shorter in patients receiving antiviral thera‐ py. Once again, in herpes encephalitis, intrathecal antibody production commences begin‐ ning from the second week. In West Nile virus encephalitis, initial neutrophylic dominance gives way to a lymphocytic pleocytosis. Capturing specific IgM antibodies in the first week after syptom onset leads frequently to negative results. But the chance of detection increases in the following days. Therefore it is crucial to repeat lumbar puncture in such cases. On the other hand, WNV RT-PCR is positive in a narrow period, but the possibility of a positive

**cell count Protein Glucose**

Cerebrospinal Fluid Abnormalities in Viral Encephalitis

http://dx.doi.org/10.5772/54590

29

**Cell count PCR Antibody production**

**HSV** MN High Normal-Low **VZV** MN High Normal-Low **CMV** MN High Normal **MUMPS** MN Normal- High Normal-Low

**Enteroviruses** Normal-MN High Normal **WNV** PNL-MN High Normal **Influenza** Normal Normal Normal **JC virus** Normal High Normal

**HSV**< 3 days Normal-mononuclear Negative Negative

**WNV** <2 days Polymorphnuclear Positive Negative 2-7 days Mononuclear Positive-Negative Negative "/>7 days Mononuclear Negative Positive

3-14 days Mononuclear Positive **Negative-**Positive "/>14 days Mononuclear **Negative-**Positive **Positive-**Negative

result decreases as the disease progresses (Table 7).

**Table 6.** CSF characteristics of encephalitis in various viruses.

**Table 7.** Time dependent alterations of CSF findings in Herpes and WNV.

As we mentioned above, a part of recent studies targets on inflammatory responses in CSF. Without question, these biomarkers are not etiology specific. However, they can be used for manifesting the severity of neuroinvasif disease. One of those markers is macrophage migra‐ tion inhibitory factor (MIF) that increases in CSF in CNS infections [16]. Studies that investi‐ gate the association of these factors with possible etiological agents and disease severity is needed (Figure 2).

**Figure 2.** Several biomarkers elevating in CSF during the course of central nervous system infections.

#### **FLAVIVIRUS INFECTIONS**

Elevated protein, high cell count (initially neutrophilic; mononuclear pleocytosis after a certain time), normal glucose concentrations

RT-PCR, IgM ELISA capture

Virus isolation

**Table 5.** CSF characteristics and diagnostic methods in flavivirus encephalitides

CSF findings in all types of encephalitis may expose time dependent alterations. In cases with negative PCR, repeated lumbar punctures should be performed, differences in cell count should be observed, PCR studies should be repeated and new cell cultures should be made for virus isolation. This aproach is valid in patients receiving amprical antiviral treat‐ ment also. For example, it is known that PCR becomes positive several days after the onset of clinical symptoms in herpes encephalitis. PCR test becomes negative after a certain time in HSV and VZV encephalitis. This duration is shorter in patients receiving antiviral thera‐ py. Once again, in herpes encephalitis, intrathecal antibody production commences begin‐ ning from the second week. In West Nile virus encephalitis, initial neutrophylic dominance gives way to a lymphocytic pleocytosis. Capturing specific IgM antibodies in the first week after syptom onset leads frequently to negative results. But the chance of detection increases in the following days. Therefore it is crucial to repeat lumbar puncture in such cases. On the other hand, WNV RT-PCR is positive in a narrow period, but the possibility of a positive result decreases as the disease progresses (Table 7).


**Table 6.** CSF characteristics of encephalitis in various viruses.

protein concentrations are usually increased, glucose levels are normal. RT-PCR is assistant, but it is not possible in late stages of the disease to capture the virus RNA [12]. Virus isola‐ tion by means of CSF cultures is also utilised [13]. Today the most valid methods are sero‐ logical approaches. The success of ELISA in detecting WNV-specific antibodies is increased in 8-21 days after the beginning of clinical symptoms. Similar serological methods can be used in other Flavivirus infections. In Japan encephalitis, for example, the valid method cur‐ rently is ELISA capture of JE-IgM [14] (Table 5). Various biomarkers, which are detected in CSF in the course of WNV encephalitis may reflect the severity of disease and neuronal damage. In 58 % of cases with WNV, NfH-SM135 and GFAP-SM126 can be found positive, S100B positivity is seen in 90 % of this same group [15]. In Eastern equine encephalitis, leu‐

so be noted that dominant cells are polymorphnuclear. CSF findings emerged from various

As we mentioned above, a part of recent studies targets on inflammatory responses in CSF. Without question, these biomarkers are not etiology specific. However, they can be used for manifesting the severity of neuroinvasif disease. One of those markers is macrophage migra‐ tion inhibitory factor (MIF) that increases in CSF in CNS infections [16]. Studies that investi‐ gate the association of these factors with possible etiological agents and disease severity is

; it should al‐

IFN-γ, TNF-α, IL-2, IL-6, CD8

NfH-SM135, GFAP-SM126

Macrophage migration inhibitory

S100B

factor (MIF)

cocyte count is much more increased, and it can reach 1000-2000 cells per mm3

**Figure 2.** Several biomarkers elevating in CSF during the course of central nervous system infections.

**Table 5.** CSF characteristics and diagnostic methods in flavivirus encephalitides

**FLAVIVIRUS INFECTIONS** Elevated protein, high cell count (initially neutrophilic; mononuclear pleocytosis after a certain time), normal glucose

encephalitic situations are summarized in Table 6.

**CNS INFECTIONS**

needed (Figure 2).

28 Encephalitis

concentrations

Virus isolation

RT-PCR, IgM ELISA capture


**Table 7.** Time dependent alterations of CSF findings in Herpes and WNV.
