CausesEstablishment

The development of purulent meningitis can be traced back to three causes. Purulent meningitisThe most common is the spread of the pathogens with the bloodstream (hematogenic meningitis). This can be the case when a bacterial infection (e.g.

of the nasopharynx (sniffles) or lungs (cough)) generalizes, i.e. the pathogens spread with the blood throughout the body. On the other hand, pathogens from a chronic suppurative focus can be repeatedly washed into the blood, for example in chronic endocarditis (inflammation of the heart muscle and heart valves = pathogens spread from the heart) or osteomyelitis (chronic bone ulceration = pathogens spread from the bone). Most common pathogens: meningococci, pneumococci, streptococci, staphylococci, enterococci

Purulent meningitis via the bloodstream (usually after droplet infection, e.g.
via cough or rhinitis)
Contaminated meningitis
Direct (secondary) meningitis

Contaminated meningitisConducted meningitis usually results from an infection of the head, e.g. an infection of the paranasal sinuses (acute or chronic), middle ear or mastoiditis (the processus mastoideus is the bone of the temporal bone behind the external auditory canal). It is a bone filled with air that is connected to the middle ear). Here, the pathogens migrate through the thin bone walls of the skull into the so-called subarachnoid space and thus lead to infection.

The subarachnoid space with its three meninges lies between the bony skull and the brain and is surrounded by cerebrospinal fluid, the so-called cerebrospinal fluid. Bacteria that enter this space through the bone first pass through the outer, hard meninges (dura mater). Underneath this lies the middle, delicate spider web (arachnoid membrane), under which the space in question is located (sub = under, sub-arachnoid = located under the spider web), which is filled with cerebrospinal fluid and from which the pathogens can easily spread over the entire surface of the brain (and spinal cord).

The lower boundary of this subarachnoid space is formed by the inner, soft meninges (pia mater), which as a delicate layer lies directly on the brain and follows it in its furrows and coils. Most common pathogens: Pneumococcus, meningococcus. Direct (secondary) meningitisEven in skull injuries such as skull base fractures, bacteria that colonize the nasopharynx and sinuses can easily migrate into the subarachnoid space, especially if the outer, hard meninges have been injured.

Finally, in the case of open skull injuries, the pathogens have direct access to the cerebrospinal fluid, so that in many cases an inflammation occurs within a short time. The most common pathogens: pneumococci, hemophilus influenzae, staphylococci. In addition to the clinically impressive and trend-setting clinical picture, the primary examination in suspected bacterial meningitis is the removal and examination of the cerebrospinal fluid (liquor).

It should be obtained before starting antibiotic therapy and examined for pathogens, cells, protein, sugar and lactate. These factors indicate the type of inflammation. Normal, healthy cerebrospinal fluid is clear as water.

It is filtered off by the blood at certain points in the brain and is then distributed within the meninges via the brain and spinal cord. It is removed by inserting a hollow needle into one of the spaces between the 3rd and 5th lumbar vertebrae in the spinal cord space below the spinal cord (lumbar puncture). The spinal fluid then drips through this needle into sterile tubes.

Its appearance alone can give an indication of the type of disease and possible pathogens: In purulent meningitis it is cloudy to purulent, in viral meningitis clear to at most somewhat cloudy. In addition to cerebrospinal fluid, blood is always examined and the two findings are compared. This examination is called liquor diagnostics (examination of the cerebrospinal fluid).

A lumbar puncture is not performed if the patient quickly becomes comatose or if there are other signs of increased intracranial pressure or signs of disturbed coagulation. To confirm the diagnosis, the pathogen is detected under the microscope after Gram staining (visualization of the pathogen in color), bacteriological detection is carried out by applying a culture. In 70-90% of the cases, pathogen detection is possible.The blood culture (blood smear on culture media) is positive in 30-50% of cases.

The blood also shows leukocytosis (accumulation of white blood cells) and an increase in CRP (C-reactive protein, CRP value), which is a non-specific marker for the course of inflammatory processes in the body. Serum procalcitonin is also elevated, in contrast to viral meningoencephalitis. A PCR (polymerase chain reaction) for the detection of bacterial DNA or the detection of bacterial antibodies is only carried out if the CSF result is unclear or the pathogen is not detected.

In addition, a CT (= computed tomography) of the head (CCT = cranium computed tomography) is usually also performed to assess the paranasal sinuses (maxillary sinus, frontal sinus, ethmoid cells) and possible foci of mastoid melting (mastoid process) from which meningitis can be transmitted. Likewise other pus foci such as a brain abscess, bleeding or infarcts (circulatory disturbance of the brain) can be recognized. The extent of the existing cerebral pressure caused by cerebral edema or hydrocephalus (hydrocephalus) can also be estimated in this way.