Encephalopathies

Question 1

Define encephalopathy

Answer 1

Altered consciousness for >24hrs
Lethargy, irritability or personality/behavioural changes

Question 2

Define encephalitis

Answer 2

Encephalopathy plus CNS inflammation
-fever
-seizures
-focal neurological signs
-CSF pleocytosis (>4 cells/uL)
-EEG features
-neuroimaging features

Question 3

Encephalitis features

Answer 3

Triad
-Altered mental status
-Fever
-Headache

Other features
-Seizures
-Focal neurological signs
-Fluctuating mental status
-Photophobia and nuchal rigidity typically absent

Relevant background
-Geographical and seasonal factors
-Travel and immigration
-Occupational exposure
-Medical history
-Immune status

Bloods
-lymphocytosis
-leucopenia
-thrombocytopenia

EEG
-Diffuse slowing, focal abnormalities

MRI brain
-focal abnormalities

LP

Question 4

Encephalopathies classic syndromes

Answer 4

Parotitis
-mumps

Flaccid paralysis or multi focal lower motor neurone signs
-West Nile (maculopapular rash)
-Polio

Hydrophobia, aerophobia, pharyngeal spasms, hyperactivity
-rabies

Grouped vesicles in dermatomal pattern, mucomembranous lesions
-VZV

Erythema nodosum
-TB
-Histoplasmosis

URTI
-influenza
-mycoplasma

Question 5

LP analysis

Answer 5

CSF pressure
-Measure in Lateral decubitus
-Normal: 60-250mmHg
-Raised: infection, bleeding, mass

WCC
-Normal: 5 WBC and 3 polymorphs
-Raised in infection, seizures, tumour, haemorrhage, traumatic tap
-Polymorphic common in bacterial and early viral. But lymphocytic uncommon in early bacterial
-Can normalise WBC for RBCs and peripheral WCC in traumatic tap

RCC
-normal is 5
-raised in SAH and traumatic tap
-RCC constant across tubes in SAH

Xanthochromia
-Pink or yellow discolouration (haemoglobin degradation)
-Occurs after 2 hours
-SAH
-TB

Protein
-normal: 18-58 mg/dL
-Raised in traumatic tap, SAH, infection, malignancies, autoimmune
-can normalise protein for RBC in traumatic tap

Glucose
-Correct for serum (0.5-0.8)
-Low (hypoglycorrhachia): infection, cancers, sarcoid
-High: hyperglycaemia

Lactate
-raised is more specific than cell count, glucose, protein for bacterial over viral

Immunoglobulins
-Almost entirely excluded from CSF normally
-Oligoclonal bands: MS, tumours, lymphoproliferative diseases

Cytology
-malignancy

Gram stain
-infection

Question 6

Viral vs bacterial LP result

Answer 6

Viral
-WCC usually <100
-lymphocytic pleocytosis (may be neutrophils if early)
-protein usually <400mg/dL
-glucose >0.5 of serum (mildly reduced sometimes)

Bacterial
-WCC >1000/uL
-Polymorph predominance
-Protein >400mg/dL
-Glucose <0.5 of serum

Question 7

Criteria for possible autoimmune encephalitis

Answer 7

Subacute onset (rapid progression over <3 months)
-Altered level of consciousness
-Short term memory loss
-Or psychiatric symptoms

At least one of the following
-Focal neuro findings
-Seizures (without seizure disorder)
-CSF pleocytosis
-MRI features of encephalitis

Reasonable exclusion of alternatives