Neutrophilic leukocytes in cytology

Cytological picture of CSF in purulent inflammation

The key criterion for diagnosing purulent infections of the central nervous system, such as purulent meningococcal meningitis, is the examination of cerebrospinal fluid. Massive tissue infiltration by neutrophilic leukocytes is accompanied by marked inflammatory plethora (hyperemia) and changes in the physical properties of the CSF.

Upon macroscopic evaluation, the fluid emerges under increased pressure, loses its transparency, becomes turbid, and acquires a whitish or characteristic yellowish-green hue.

Cytological examination reveals a massive neutrophilic pleocytosis:

• The total cell count ranges from 500 to 1,000 or more per 1 µL.
• The proportion of neutrophilic leukocytes in the cell pool reaches 60–100%.
• In extremely severe, pronounced cases of the process, cytosis can reach 4- or even 5-digit levels.

During bacterioscopy of stained smears, the detection of Gram-negative diplococci becomes a crucial diagnostic sign. Microorganisms are located not only extracellularly but also inside the neutrophils themselves, reflecting an active process of incomplete or complete phagocytosis.

Associated biochemical and hematological changes

Cytological findings are always evaluated in conjunction with biochemical CSF parameters and a complete blood count (hemogram).

In the cerebrospinal fluid against the background of the neutrophil pool, cyto-protein dissociation is observed: the protein level rises to 2–8 g/L. Concurrently, an increase in lactate concentration and a decrease in glucose levels are recorded, which is associated with the active metabolism of bacteria and the leukocytes themselves.

The systemic reaction of the body is manifested in the complete blood count:

1. Neutrophilic leukocytosis occurs.
2. A left shift of the leukocyte formula is observed (appearance of immature neutrophil forms).
3. Thrombocytopenia is recorded.
4. The erythrocyte sedimentation rate (ESR) is significantly increased.

In the event of a generalized form (meningococcemia), the cytological reaction of the blood becomes extreme: neutrophilic hyperleukocytosis develops with a sharp left shift and a stably high ESR.

Differential diagnosis by cytogram

The evaluation of neutrophils in CSF requires careful differentiation from other pathologies. Differential diagnosis is carried out with serous and purulent meningitis of other etiologies, brain abscesses, and subarachnoid hemorrhage.

List of pathogens that need to be ruled out:

• Bacteria: pneumococci, Haemophilus influenzae, streptococci, staphylococci, Klebsiella, Escherichia, Salmonella, Listeria, Leptospira, spirochetes, Mycobacterium tuberculosis.
• Viruses: Coxsackie, ECHO, mumps virus.

Final verification is achieved via lumbar puncture with comprehensive biochemical, bacteriological, immunological, and molecular-genetic testing.

Particular attention should be paid to differentiation from meningismus. In meningismus, the clinical picture may simulate meningitis, but signs of true inflammation in the CSF are completely absent. Macroscopy, biochemistry, and the cytogram remain within normal limits; only a very slight increase in cytosis without massive neutrophilic infiltration is permissible.

Clinical and anatomical syndromes

Purulent neutrophilic inflammation of the meninges and brain tissue (meningoencephalitis) forms four main clinical syndromes: intoxication, cerebral, meningeal, and focal neurological deficit syndromes.

Due to the anatomical proximity of the affected meninges and the underlying brain tissue, as well as the commonality of the inflammatory process, it can be difficult to distinguish between meningitis and meningoencephalitis. Focal symptoms manifest very early—within the first 24–48 hours:

• Brainstem disorders: ptosis, diplopia, gaze palsy, convergence disturbance, and pupillary signs.
• Vestibular disorders: ataxia, dizziness, nystagmus.
• Motor impairments (less frequently): spastic hemi- and monoparesis, hyperkinesia, appearance of pathological reflexes (Babinski reflex).

An important diagnostic marker of a mixed form of infection (meningitis + meningococcemia) is the detection of a characteristic hemorrhagic rash. It presents as dense-to-the-touch "starry" spots of various shapes and sizes, emerging against the background of a pronounced meningeal syndrome.

What else to study on this topic

• Mechanisms of post-infectious immunity formation in generalized forms and reasons for the rarity of relapses.
• Specific prevention: polysaccharide vaccines (J07AH), duration of their protection, and epidemiological efficacy.
• Pathogenesis of cyto-protein dissociation in cerebrospinal fluid.
• Features of phagocytosis of Gram-negative diplococci by neutrophils.

Other topics in the "Additional Topics" section

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