Intracranial Infections and Neurosyphilis

Intracranial infections can lead to cognitive impairments; treatment is often effective.
Consider unusual infections as potential causes of unexplained cognitive and psychiatric symptoms.
Types of infections include encephalitis and HIV, which are covered in separate chapters.

Caused by Treponema pallidum, neurosyphilis is uncommon in Western countries but rising in Eastern Europe and among those with HIV.
Symptoms appear in neuropsychiatric patients; blood or CSF tests are recommended for diagnosis.
Asymptomatic stages can precede clinical manifestations, with variable latencies.
Forms of symptomatic neurosyphilis:
- Meningovascular syphilis: Occurs within 5 years of infection leading to strokes, personality changes, headaches, and possible dementia.
- General paresis: Develops around 20 years post-infection; causes dementia, personality changes, dysarthria, and may feature grandiose delusions.
- Tabes dorsalis: Involves degeneration of spinal cord pathways; less common in psychiatric settings.

Brain tumours can significantly impact psychological health, often presenting with psychological symptoms.
Slow-growing tumours in 'silent' areas (e.g., frontal lobe) may cause psychological effects without noticeable neurological signs.
Symptoms are influenced by raised intracranial pressure and rate of tumour growth.
Rapidly growing tumours can cause delirium; slower tumours may lead to chronic cognitive deficits.
Specific neuropsychiatric syndromes arise from focal lesions, particularly near frontal poles, which may lead to personality changes.
Tumours near the hypothalamus are associated with personality alterations and apathy.
Cognitive impairments post-treatment for brain tumours, especially in children who received radiotherapy, are notable concerns.

Neoplasms can impair cognition through various mechanisms beyond direct brain tumour effects.
Cognitive issues may arise during treatment or may present as initial symptoms.
Common causes of cognitive impairment in cancer patients include:
- Mass effects: Primary and metastatic brain tumours, haemorrhagic changes, and meningeal conditions.
- Metabolic derangements: Conditions like hypercalcaemia, hyponatraemia, acidosis, and hypoglycaemia.
- Radiotherapy effects: Can lead to radionecrosis, cerebral atherosclerosis, and leucodystrophy.
- Chemotherapy: May cause metabolic encephalopathies and increase susceptibility to opportunistic infections.