A prospective study to determine the value of cerebrospinal fluid analysis in the differential diagnosis of meningitis was performed in 710 consecutively observed patients, both children and adults, who underwent lumbar puncture due to suspected central nervous system infection. Diagnoses included acute or presumed bacterial meningitis (n = 79), acute or presumed viral meningoencephalitis (n = 218), acute unclassified meningitis (n = 6), other infections of the central nervous system (n = 37), non-infectious neurological diseases (n = 76) and control patients (n = 294). The sensitivity, specificity and predictive values were determined for cerebrospinal fluid white blood cell count, total protein, lactate, glucose and C-reactive protein levels as well as the blood/cerebrospinal fluid glucose ratio. Determination of cerebrospinal fluid levels of lactate (greater than or equal to 3.5 mmol/l) was found to be superior to the other tests. The C-reactive protein level gave no additional diagnostic information when the lactate level was determined. The white blood cell count, and total protein and glucose levels were often unreliable tools for differential diagnosis, largely due to low sensitivity at realistic discriminatory limits. The study confirms that no cerebrospinal fluid test is fully reliable in distinguishing bacterial meningitis from other forms of meningitis.
Allodynia is a well-known component of neuropathic pain resulting from injury to the nervous system. Clinical pain states with allodynia in connection with longstanding superficial wounds have, however, not been reported in the literature. In this case a chronic pain state developed in a previously healthy 17-year-old girl in and around a persistently suppurating appendectomy wound. There was no spontaneous pain but pronounced allodynia in the wound and in the surrounding skin. Quantitative thermal tests showed abnormal thresholds for several sensory modalities confirming abnormal processing of sensory input from the involved area. The pattern of sensory abnormalities evaluated with thermal testing changed transiently and the allodynia diminished during a phentolamine block. Since the pain responded poorly to opioids and ketamine has been reported to reduce allodynia, it was administered in a sub-dissociative bolus dose during wound dressing. The wound was essentially unchanged after treatment for 3 months but the allodynia and sensory aberrations had decreased significantly. We interpret these results as a de-sensitizing effect in the long term of repeated NMDA-receptor blockade by ketamine in a chronic pain state, with indications of central sensitization, partially maintained by sympathetic activity.
The ability of serum C-reactive protein (S-CRP) to differentiate between acute bacterial and viral meningitis was evaluated in 235 patients, both children and adults. The patients underwent lumbar puncture due to suspected central nervous system (CNS) infection. In patients with bacterial meningitis, 7/60 (12%) had S-CRP concentrations below 50 mg/l. Of these patients, 4 were children below 6 years of age, all with symptoms of meningitis for less than 12 h before admission and 3 adults of whom 1 had symptoms of meningitis for less than 12 h. In patients with viral meningitis, 15/146 (10%) had S-CRP concentrations above 50 mg/l. Only 3 children below 6 years of age with viral meningitis had S-CRP concentration above 20 mg/l, but none exceeded 50 mg/l. An S-CRP value above 50 mg/l in patients with CSF pleocytosis usually indicates bacterial etiology. However, S-CRP values above 50 mg/l may occasionally be seen in viral meningitis. In children younger than 6 years of age a discriminatory level for S-CRP of 20 mg/l can be used to distinguish between bacterial and viral meningitis, but for older patients a discriminatory level of 50 mg/l is more appropriate. If the duration of the illness is less than 12 h, S-CRP concentrations below the discriminatory levels are of limited diagnostic value.
Acyclovir-induced neuropsychiatric symptoms (AINSs) may resemble several diseases of the central nervous system. Laboratory testing of acyclovir may be critical in supporting the diagnosis of AINSs when there is doubt. We present a case of suspected herpes encephalitis in which the diagnosis of AINSs was supported by therapeutic drug monitoring of plasma and cerebrospinal fluid concentrations of acyclovir and its main metabolite 9-carboxymethoxymethylguanine.
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