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1. Role of CT Brain in Infectious Diseases Presenter: [Dr Samim Amin] MBBS Karachi Pakistan House job Karachi Pakistan FCPS Training in diagnostic and interventional radiology from gangal ram hospital/Fatima jinnah medic institute Lahore Pakistan MRCS (UK) and registered with GMC Affiliation: Mellat medical complex

2. Introduction CT Brain is a vital imaging tool in the diagnosis and management of infectious diseases involving the central nervous system (CNS). Timely imaging can identify complications and guide interventions. Speaker Notes: CT plays a crucial role in rapidly identifying CNS infections and their complications like abscesses, hydrocephalus, or infarcts. It’s often the first imaging modality due to speed and accessibility.

3. Objectives Understand indications for CT Brain in suspected CNS infections. Review key infectious diseases detectable by CT. Discuss CT findings and their clinical implications. Compare CT with MRI where appropriate.

4. When to Use CT Brain in Infections Suspected meningitis with altered mental status or focal signs. Seizures , especially new-onset. Fever with neurological symptoms . Immunocompromised patients (e.g., HIV, transplant). Evaluate headache in infection context.

5. Common CNS Infections Assessed by CT Pyogenic brain abscess Tuberculous meningitis Neurocysticercosis Toxoplasmosis Encephalitis Subdural empyema Fungal infections T:  toxoplasmosis O:  other (e.g.  syphilis ,  varicella-zoster ,  parvovirus B19 ) R:  rubella C:  cytomegalovirus (CMV)  - most common H:  herpes simplex virus (HSV)

6. Pyogenic Brain Abscess CT Features: Ring-enhancing lesion with central hypodensity. Surrounding edema. Mass effect or midline shift. Speaker Notes: CT with contrast is essential. A well-defined ring with a hypodense center indicates necrotic tissue. It's important to differentiate from tumors or metastases.

7. Tuberculous Meningitis (TBM) CT Findings: Basal meningeal enhancement. Hydrocephalus. Infarcts in basal ganglia due to vasculitis. Tuberculomas : isodense or hypodense with ring or nodular enhancement. Speaker Notes: TBM often presents subtly. CT helps in detecting complications like hydrocephalus early, which may require surgical intervention.

8. Neurocysticercosis CT Phases: Vesicular (cystic with no edema) Colloidal vesicular (ring enhancement, edema) Granular nodular (nodular enhancement) Calcified (hyperdense foci without edema) Speaker Notes: The stage of the cyst determines treatment and prognosis. CT is excellent for detecting calcifications in the later stages.

9. Toxoplasmosis Seen in immunocompromised patients (e.g., HIV). Multiple ring-enhancing lesions. Predominantly in basal ganglia and corticomedullary junction. Speaker Notes: Differential includes CNS lymphoma. Clinical correlation and response to treatment often help in differentiation.

10. cortical abnormalities are present, but 

11. Other associated findings are: cerebral / cerebellar  atrophy encephalomalacia cortical and subcortical chunky calcifications ventriculomegaly microcephaly  or  m acrocephaly  due to  hydrocephalus

12. Herpes Simplex Encephalitis Early CT may be normal. Later changes: Hypodensities in temporal lobes. Hemorrhagic changes. Edema and mass effect. Speaker Notes: MRI is more sensitive, but CT can detect late-stage changes and guide urgent care, especially in emergencies.

13. Subdural Empyema Crescentic extra-axial fluid collection. Hyperdense or isodense compared to CSF. Mass effect, often with midline shift. Speaker Notes: Usually arises from sinusitis or otitis media. Surgical drainage is often needed, and CT helps assess urgency.

14. Fungal Infections Common in immunocompromised. Aspergillosis and mucormycosis : Infarcts. Hemorrhagic lesions. Enhancing masses or abscesses. Speaker Notes: CT can help detect bony involvement, especially in rhino-cerebral mucormycosis , which often spreads from sinuses.

15. Advantages of CT Brain Rapid and widely available. Good for detecting: Hydrocephalus Hemorrhage Mass effect Calcifications

16. imitations of CT Less sensitive for early meningitis or encephalitis. Poor soft tissue contrast. Radiation exposure. MRI is preferred for detailed parenchymal imaging.

17. Feature CT MRI Speed Fast Slower Soft Tissue Detail Moderate Excellent Calcifications Excellent Moderate Meningeal Enhancement Limited Superior Cost/Availability Lower Higher T vs MRI in CNS Infections

18. Conclusion CT Brain plays a pivotal role in the initial evaluation and management of CNS infections. Early recognition of complications saves lives. While MRI is superior for soft tissue detail, CT remains a first-line tool in emergencies and resource-limited settings.

19. References Barkovich AJ. Pediatric Neuroimaging. Osborn AG. Diagnostic Imaging: Brain. WHO guidelines on TB and HIV-associated CNS infections. Recent journal articles (optional).

20. Q&A “Thank you! Questions and discussions welcome.”