Headache of variable duration caused by bacterial meningitis or meningoencephalitis. It may develop in a context of mild flu-like symptoms. It is typically acute and associated with neck stiffness, nausea, fever and changes in mental state and/or other neurological symptoms and/or signs. In most cases it resolves once the infection has been eradicated, but rarely it becomes persistent.
A. Headache of any duration fulfilling criterion C
B. Bacterial meningitis or meningoencephalitis has been diagnosed
C. Evidence of causation demonstrated by at least two of the following:
1. headache has developed in temporal relation to the onset of the bacterial meningitis or meningoencephalitis
2. headache has significantly worsened in parallel with worsening of the bacterial meningitis or meningoencephalitis
3. headache has significantly improved in parallel with improvement in the bacterial meningitis or meningoencephalitis
4. headache is either or both of the following:
b) located in the nuchal area and associated with neck stiffness
D. Not better accounted for by another ICHD-3 diagnosis.
Headache is the commonest and may be the first symptom of these infections. 9.1.1 Headache attributed to bacterial meningitis or meningoencephalitis should be suspected whenever headache is associated with fever, altered mental state (including reduced vigilance), focal neurological deficits or generalized seizures. In the case of encephalitis, associated deficits include disturbances of speech or hearing, double vision, loss of sensation in some parts of the body, muscle weakness, partial paralysis in the arms and legs, hallucinations, personality changes, impaired judgment, loss of consciousness, sudden severe dementia and/or memory loss.
Nevertheless, in most cases of intracranial bacterial infection it is extremely difficult to distinguish involvement purely of the meninges from involvement purely of the encephalon. Furthermore, this distinction does not lead to different approaches to evaluation or choice of treatment. Therefore, headache attributed to bacterial meningitis and headache attributed to bacterial encephalitis have been included in the same subgroup of 9.1.1 Headache attributed to bacterial meningitis or meningoencephalitis.
A variety of microorganisms may cause meningitis and/or encephalitis, including Streptococcus pneumoniae, Neisseria meningitides and Listeria monocytogenes.
Direct stimulation of the sensory terminals located in the meninges by the bacterial infection causes the onset of headache. Bacterial products (toxins), mediators of inflammation such as bradykinin, prostaglandins and cytokines and other agents released by inflammation not only directly cause pain but also induce pain sensitization and neuropeptide release. In the case of encephalitis, increased intracranial pressure may also play a role in causing headache.
In most of cases, headache remits with resolution of the infection. However, the infection may remain active for months, leading to chronic headache. In a minority of cases, headache persists for more than three months after resolution of the causative infection. Three separate subforms of 9.1.1 Headache attributed to bacterial meningitis or meningoencephalitis are therefore described below because pathophysiology and treatment are different depending on whether the infection has been completely eradicated or remains active.