Lactic dehydrogenase in cerebrospinal fluid may differentiate between structural and non-structural central nervous system lesions in patients with diminished levels of consciousness.

BACKGROUND

Impaired consciousness without a history of trauma is a common reason for emergency department (ED) visits. Among critically ill patients with a history and physical findings suggestive of a cerebrovascular accident (CVA), it may be difficult to differentiate between a structural and a non-structural cause for their condition.

OBJECTIVES

This study was conducted to determine if lactic dehydrogenase (LDH) levels in the cerebrospinal fluid (CSF) of patients with acute non-traumatic neurological disorders could distinguish between structural and non-structural etiologies.

MATERIAL AND METHODS

Over a 6-month period, CSF specimens were collected from 54 critically ill patients admitted to the ED with impaired consciousness and findings consistent with a CVA. The patients had moderate to severe impairment of consciousness, had a new motor or sensory deficit, or had meningeal signs of recent onset. CSF-LDH levels were analyzed because CSF levels of the enzyme are typically elevated in meningitis, metastatic cancer, and disorders resulting in ischemic necroses. Patients were excluded if a computed tomography scan showed contraindications to performing a lumbar puncture, if they had a coagulopathy, or if the CSF was xanthochromic or produced visible blood sediment after centrifuging. The data were analyzed according to the patients' admission diagnoses-structural vs. non-structural lesion.

RESULTS

Of the samples collected from 54 patients, eight were excluded. Among the 46 patients included in the study, the mean age was 56.1 +/- 2.75 years, mean APACHE II score was 20.93 +/- 0.98, Glasgow Coma Scale (GCS) score was 7.15 +/- 0.49, and mortality was 55% (22 patients). The 30 patients with a structural abnormality had a mean age of 56.7 +/- 3.55 years, GCS score of 7.3 +/- 0.61, APACHE II score of 20.2 +/- 1.1, mortality of 43% (13 patients), and CSF-LDH level of 128.8 +/- 24.8 IU/L (95% confidence interval [CI] 78.1-179.6). The 16 patients with a non-structural (metabolic) disturbance had: a mean age of 55.0 +/- 4.42 years, GCS score of 6.87 +/- 0.86, APACHE II score of 22.2 +/- 1.94, mortality of 56% (9 patients), and CSF-LDH level of 29.8 +/- 2.9 IU/L (95% CI 23.6-36.1). Analysis by Student's t-test was p < 0.05. When the diagnostic value of CSF-LDH level was evaluated using a cutoff point of 40 IU/L, the following results were obtained: sensitivity: 86.7%, specificity: 81.3%, pretest likelihood: 65%, positive predictive value: 90%, negative predictive value: 76%, Likelihood Ratio (LR)+: 4.62, LR-: 0.16 (6.25-fold increase).

CONCLUSIONS

In critically ill patients with acutely altered levels of consciousness but without a history of trauma, a CSF-LDH value < or = 40 IU/L is associated with non-structural pathology.