Table 3.

Approach to investigating acute and or chronic cognitive dysfunction

ModalityTestConditions
BloodsFull blood count, urea and electrolytes, calcium, B12, folate, thyroid function tests, cortisol, liver function tests, ammonia, HIV, microscopy and culture, arterial blood gas, glucoseAnti-thyroid peroxidase antibody, thyroid-stimulating hormoneAnti-nuclear IgG antibodiesdsDNA, Sm/RNP, Ro52, Ro60, La (SS-B), Scl-70, centromere, Mi-2, Ku, Th/To, RNA Pol III, Pm-Scl and proliferating cell nuclear antigen, Jo-1 and ribosomal-PAnti-neutrophil cytoplasmic IgG antibodies screenAnti-glutamic acid decarboxylase IgG antibodyAnti-nuclear IgG antibodies by indirect immunofluorescence (HEp-paraneoplastic IgG antibody screen)Voltage gated potassium channel antibodiesInfection, anaemia, electrolyte imbalance, dehydration, liver failure, renal failure, endocrinopathy, vitamin deficiency, septicaemia, hypoxia, hypercapnia, acid base disorders, glycaemic disorders, autoimmune encephalitis
UrineUrine analysis, microscopy and culture, toxicology screenUrinary tract infection, drug toxicosis
UltrasoundBladder, kidney-ureter-bladder, echocardiographyUrinary retention, urinary tract infection, subacute bacterial endocarditis
X-rayChest, musculoskeletalPneumonia, heart failure, fracture
NeuroimagingCT head, MRI head, DaTSCANStroke, haemorrhage, structural lesions, dementia with Lewy bodies
Computed tomographyChest, abdomen and pelvisSuspecting malignancy
Magnetic resonance imagingDWI, FLAIRSOL, Alzheimer's disease, CVA
Lumbar punctureCSF proteinCSF glucoseCSF TPO, M/C/SOligoclonal bandsNMDA receptor antibodiesVoltage gated calcium channel antibodiesVoltage gated potassium channel antibodiesCSF (s100, p 14-3-3) in CJDMeningitis, encephalitis
ElectroencephalographyPseudo periodic triphasic complexes may be present progressive disease in prion disease (CJD)Delirium, metabolic eg hepatic encephalopathy, epilepsy
DaTSCANReduced ioflupane uptakeDementia with Lewy bodies
  • CJD = Creutzfeldt-Jakob disease; CSF = cerebrospinal fluid; CT = computed tomography; CVA = cerebrovascular disease; DWI = diffusion-weighted imaging; FLAIR = fluid-attenuated inversion recovery; HEp = human epithelial cells; IgG = Immunoglobulin G; MRI = magnetic resonance imaging; NMDA = N-methyl-D-aspartate; SOL = space-occupying lesion; TPO = thyroid peroxidase