Summary CNS pathology.pdf

LAST MINUTE REVISION OF CNS PATHOLOGY Intracranial Space-Occppying Lesions lecture name Intracranial Space Occupying Lesions Overview Intracranial space-occupying lesions result from a variety of causes that lead to increased intracranial volume, and can either be diffus...

LAST MINUTE REVISION OF CNS PATHOLOGY Intracranial Space-Occppying Lesions lecture name Intracranial Space Occupying Lesions Overview Intracranial space-occupying lesions result from a variety of causes that lead to increased intracranial volume, and can either be diffuse or focal. Common origins include cerebral abscesses, intracranial hematomas, and neoplasms. Consequences of Intracranial Space Occupying Lesions Raised Intracranial Pressure: Manifests as papilloedema, nausea, headache, and changes in consciousness level. Intracranial Shift and Herniation: These conditions may follow procedures like cerebrospinal fluid (CSF) withdrawal and can lead to fatal displacement of midline structures in the brain. Types of Cerebral Edema Vasogenic Edema: Occurs due to the breakdown of the blood-brain barrier leading to increased vascular permeability. Cytotoxic Edema: Caused by cellular injury affecting neurons and glial cells. Interstitial Edema : due to damage of ventricular lining in hydrocephalus Intracranial Herniation Potential sites for herniation include the cingulate gyrus, hippocampal uncus, and parahippocampal gyrus. Transtentorial Herniation: Particularly dangerous due to its propensity to compress the brainstem, frequently resulting in fatality. Epilepsy Related to Intracranial Lesions Seizures associated with these lesions can be either focal or generalized. Particularly prevalent in cases involving cerebral abscesses and neoplasms. Hydrocephalus: Accumulation of CSF Caused by the excessive accumulation of CSF, leading to disturbed flow. Hydrocephalus is categorized into primary (related to obstruction or excessive CSF production) and secondary (a consequence of brain tissue loss). Systemic Effects Can lead to severe, life-threatening systemic complications due to autonomic imbalance and subsequent organ damage. Includes conditions such as hypertension, pulmonary edema, and gastrointestinal or urinary tract complications. Specific Types and Causes of Hydrocephalus Primary Hydrocephalus: May occur from obstructions within the CSF pathways or from overproduction of CSF, potentially due to pathologies like choroid plexus neoplasms. Obstructive Hydrocephalus: Can be either congenital or acquired, often caused by structural anomalies like aqueductal stenosis. CNS Infections lecture name Routes of Infection to the CNS Pathways: Direct spread from nearby infections or through open skull fractures. Hematogenous spread from systemic infections like bacterial endocarditis. Iatrogenic introduction during medical procedures. Common Organisms: Includes risks from organisms such as S. epidermidis introduced during procedures like lumbar punctures. Bacterial CNS Infections Bacteria can access the central nervous system (CNS) through various means, including direct spread, septicemia, and iatrogenic infection. Bacterial meningitis involves inflammation in the subarachnoid space and necessitates the examination of cerebrospinal fluid (CSF) by lumbar puncture. Leptomeningitis and Meningococcal Meningitis Leptomeningitis can result from the bloodborne spread of infection with specific pathogens in different age groups. Meningococcal Meningitis Prevalence: Most common form of meningitis, can be sporadic or epidemic. Pathogens: Caused by Neisseria meningitidis, with different subgroups associated with different types of outbreaks. Spread and Complications: Transmitted via droplets from nasal carriers and can lead to severe complications like disseminated intravascular coagulation. Pachymeningitis Etiology: Often results from the direct spread of infection from cranial structures or complications of a skull fracture. Pathogens Involved: Gram-negative bacilli, haemolytic streptococci, or mixed organisms including Staphylococcus aureus. Complications: May lead to epidural or subdural abscess. Epidural and Subdural Abscess Location and Impact: Epidural abscess occurs between the dura mater and skull, acting as space-occupying lesions. Treatment: Requires surgical intervention and antibiotic therapy. Healing Process: Generally results in healing by fibrosis. Bacterial Meningitis Complications Complications of bacterial meningitis include cerebral infarction, obstructive hydrocephalus, and cerebral abscess. Cerebral Abscesses Causes: Direct spread from paranasal sinuses or middle ear infections. Septic sinus thrombosis from infections in the mastoid cavities. Hematogenous spread from conditions like infective endocarditis. Common Sites: Primarily found in the parietal lobes, often presenting as multiple abscesses.. CNS Tuberculosis CNS tuberculosis commonly stems from infection elsewhere in the body and can present as meningitis or tuberculomas. Viral Encephalitis Viral infections can reach the CNS through hematogenous or neural spread, causing conditions like meningitis or encephalitis. Severity: Typically mild but can be fatal (e.g., rabies, herpes simplex). Pathophysiology: Involves cell lysis and neuronophagia. Diagnostic Markers: Presence of viral inclusions such as 'owl-eye' in cytomegalovirus infection or Negri bodies in rabies. Rare CNS Infections Uncommon organisms like Cryptococcus neoformans, Trypanosoma rhodesiense, or Toxocaracanis can cause distinct CNS infections, especially in immunosuppressed patients. Immunosuppressed patients are at a higher risk for various infections, such as atypical mycobacteria and Candida albicans.