Infections of the Nervous System Flashcards
What is inflammation of the meninges known as?
Meningitis
What is inflammation of the brain substance known as?
Encephalitis
What is inflammation of the spinal cord known as?
Myelitis
What is the classic triad of symptoms of meningitis?
Fever
Neck stiffness
Altered mental status
What are the characteristics of meningitis?
Patients present with a short history of progressive headache associated with fever and meningism (neck stiffness, photophobia, N&V)
Cerebral dysfunction (confusion, delirium, declining consciousness level)
Cranial nerve palsy
Seizures
Focal neurological deficits
Petechial skin rash (Tumbler test)
What are the bacterial and viral causes of meningitis?
Bacterial- Nesseria meningitidis
Streptococcus pneumoniae
Viral- enteroviruses
What are the clinical features of encephalitis?
Flu-like prodrome
Progressive headache associated with fever
Potential meningism
Progressive cerebral dysfunction (confusion, abnormal behaviour, memory disturbance, depressed conscious level)
Seizures
Focal symptoms/signs
What are the causes of meningitis?
Infective- viral, bacterial, fungal
Inflammatory- sarcoidosis
Drug induced- NSAIDs, IVIG
Malignant- metastatic haematological
What are the causes of encephalitis?
Infective- viral (most commonly HSV)
Inflammatory- limbic encephalitis
Metabolic- Hepatic, uraemic, hyperglycaemic
Malignant- Metastatic, paraneoplastic
What two antibodies cause auto-immune encephalitis?
Anti-VGKC (voltage gated potassium channel)
Anti-NMDA receptor
What are the characteristics of auto-immune encephalitis that is mediated by anti-VGKC antibodies?
Frequent seizures
Amnesia
Altered mental state
What are the characteristics of auto-immune encephalitis that is mediated by anti-NMDA receptor antibodies?
Flu like prodrome
Prominent psychiatric features
Altered mental state and seizures
Progresses to movement disorder and coma
What tests can be used when investigating meningitis?
Blood cultures (bacteraemia) Lumbar puncture (CSF culture/microscopy)
What tests can be used when investigating encephalitis?
Blood cultures
Imaging- CT scan with additional MRI if necessary
Lumbar puncture
EEG
What features would indicate the need for a CT scan before a lumbar puncture?
Focal neurological deficit- not including cranial nerve palsies New onset seizures Papilloedema GCS <10 Severe immunocompromised state
What are the difference in findings in CSF in bacterial and viral meningitis?
Bacterial: -Increased opening pressure -High cell count, mainly neutrophils -Reduced glucose -High protein Viral: -Normal/increased opening pressure -High cell count, mainly lymphocytes -Normal glucose --Slightly increased protein
How is herpes simplex encephalitis diagnosed?
Lab diagnosis by PCR of CSF for viral DNA
How is herpes simplex encephalitis treated?
Treat with aciclovir on clinical suspicion
What feature of a history is relevant to arbovirus encephalitides?
Travel abroad
What is a brain abscess?
A localised area of pus within the brain
What is subdural empyema?
A thin layer of pus between the dura and arachnoid mater
What are the clinical features of brain abscess/empyema?
Fever
Headache
Focal symptoms- seizures, dysphagia etc
Signs of raised intracranial pressure- papilloedema, false localising signs, depressed conscious level
Mengism may be present, particularly for empyema
Signs of underlying source eg sinus, dental or ear infection
What are the causes of brain abscess/empyema?
Penetrating head injury
Spread from adjacent infection
Blood borne infection
Neurosurgical procedure
What investigations can be used in brain abscess/empyema?
CT or MRI
Investigate source
Blood cultures
Biopsy- drainage of pus
How is a brain abscess managed?
Surgical drainage if possible
Penicillin or ceftriaxone to cover streps
Metronidazole for anaerobes
What infections are common in HIV patients with low CD4?
Cryptococcus neoformans Toxoplasma gondii Progressive multifocal leukoencephalopathy Cytomegalovirus HIV-encephalopathy
What tests can be done in cases of suspected HIV related brain infection?
Cryptococcal antigen
Toxoplasmosis serology
CMV PCR
HIV PCR
What is the causative organism of Lyme disease?
Borrelia burgdorferi
What is the causative organism of leptospirosis?
Leptospira interrogans
What is the causative organism of syphilis?
Treponema pallidum
What are the characteristics of the first stage of Lyme disease infection?
Early localised infection
Expanding rash at site of tick bite
50% flu-like symptoms
What are the characteristics of the second stage of Lyme disease?
Early disseminated infection
One or more organ systems may become involved through haematologic or lymphatic spread
Musculoskeletal and neurologic involvement common
What are the characteristics of the third stage of Lyme disease?
Chronic infection
Musculoskeletal and neurologic involvement common
How is Lyme disease investigated?
Complex range of serological tests
CSF lymphocytosis
MRI brain/spine
Nerve conduction studies/EMG
How is Lyme disease treated?
Prolonged antibiotic treatment
How is rabies encephalitis diagnosed?
PCR and serology
What is the causative organism of tetanus?
Clostridium tetani
What is the clinical presentation of botulism?
Incubation period 4-14 days Descending symmetrical flaccid paralysis Pure motor Respiratory failure Autonomic dysfunction
How is botulism diagnosed?
Nerve conduction studies
Mouse neutralisation bioassay for toxin in blood
Culture from debrided wound
How is botulism treated?
Anti-toxin
Penicillin/ metronidazole
Radical wound debridement
What is the causative organism of botulism?
Clostridium botulinum
What are the clinical features of sporadic Creutzfeldt-Jakob disease?
Insidious onset (usually 60+) Early behavioural abnormalities Rapidly progressive dementia Myoclonus Progressing to global neurological decline Motor abnormalities Cortical blindness Seizures may occur
How is Creutzfeldt-Jakob disease investigated?
MRI-Pulvinar sign in new variant CJD, no changes in sporadic
EEG- Generalised periodic complexes common, often normal in early stages
CSF- Normal or raised protein, immunoassay 14-3-3 brain protein
