Focal CNS Infections

Anatomic Relationships of the Meninges Bone – Epidural Abscess Dura Mater – Subdural Empyema Arachnoid – Meningitis Pia Mater Brain

Anatomic relationships of the Brain Frontal Lobe – Frontal and Ethmoidal Sinuses Sella Turcica – Sphenoidal sinuses Temporal Lobe – Middle Ear, Mastoid, Maxillary Sinuses Cerebellum, Brain Stem – Middle Ear, Mastoid

Brain Abscess 50% - Local Source – otitis media, sinusitis, dental infection 25% Hematogenous spread – adults - lung abscess, bronchiectasis and empyema – children - cyanotic congenital heart disease (4-7%) – pulmonary AVM - Osler-Weber-Rendu syndrome (5%) – rarely bacterial endocarditis 10% trauma / surgery

Brain Abscess - pathology Location – temporal > frontal > other lobes >10% are multiple Stages - based on histologic findings – 1. Early cerebritis - poorly demarcated from surrounding brain – 2. Late cerebritis - reticular marix (collagen precursor) and developing necrotic center – 3. Early capsule formation - neovascularity, necrotic center, developing capsule – 4. Late capsule formation - collagen capsule, necrotic center, gliosis surrounding capsule

Subdural Empyema Located in the potential space between the dura and the arachnoid. May spread rapidly due to lack of anatomical boundaries. Less mass effect than brain abscess Surgical Emergency Usually from a local source of infection – >50% stem from a paranasal sinusitis (fronto-ethmoidal) – trauma or surgery – progression of an epidural abscess, ostermyelitis

Etiologies of SDE paranasal sinusitis % otitis-14% post neurosurgical - 4% trauma -3% meningitis (mainly peds) - 2% congenital heart disease - 2% other 7%

Intracranial Epidural Abscess Localized between dura and bone sharply defined - mainly be dural adherence to bone at suture lines focal osteomyelitis associated with subdural empyema Management and etiology same as subdural empyema

Spinal Epidural Abscess -source Hematogenous spread – Skin infections – Parenteral infections (IVDA) – Bacterial endocarditis – UTI – Respiratory infection – Dental abscess

Spinal Epidural Abscess -source direct – decubitus ulcer – psoas abscess – trauma – pharyngeal infection – mediastinitis – pyelonephritis

Spinal Epidural Abscess -source Following spinal procedures – open procedure for example disectomy – closed procedure LP Epidural catheter No source in 50% of patients in some series

Spinal Epidural Abscess - location Cervical – 15% Thoracic - 50% Lumbar - 35% Posterior to the Cord - 82%

Parasitic Infections - Cysticercosis Most common parasitic infection in CNS – Caused by larval stage of Taenia solium- pork tapeworm – Incubation period from months to decades 83% of cases show symptoms within 7 years of exposure

Parasitic Infections - Cysticercosis Common routes of infection – Food (usually vegetables) or water containing eggs from human feces – Fecal - Oral autoinfection (poor sanitation habits) – Autoinfection from reverse peristalsis - (theory possibly offered by patients who autoinfected themselves)

Parasitic Infections - Cysticercosis cystercercus cellulosae - (3-20 mm) – regular round thin walled cyst, – produces only mild inflammation – larva in cyst cystercercus racemosus - (4-12 cm) – active growing – grape like clusters – intense inflammation – no larva in cyst

Parasitic Infections - Cysticercosis Location: – meningeal 27-56% – parenchymal 30-63% – ventricular 12-18% (may cause hydrocephalus) – mixed - 23% Clinical – symptoms of increased intracranial pressure

Parasitic Infections - Cysticercosis serology – antibody titers significant if 1:64 in the serum and 1:8 in the CSF CT scan – ring enhancing / calcified lesions, multiple

Fungal Infections Cryptococcosis - most common fungal infection in CNS diagnosed in live patients – Cryptococcoma (mucinous pseudocyst) - occurs almost entirely in the HIV population – 3-10mm, most commonly in the basal ganglia Candidiasis - most common fungal infection in CNS diagnosed in dead patients – rare in healthy individuals Aspergillosis Coccidiomycosis - normally causes meningitis