Approach to investigating acute and or chronic cognitive dysfunction
| Modality | Test | Conditions |
|---|---|---|
| Bloods | Full 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 antibodies | Infection, anaemia, electrolyte imbalance, dehydration, liver failure, renal failure, endocrinopathy, vitamin deficiency, septicaemia, hypoxia, hypercapnia, acid base disorders, glycaemic disorders, autoimmune encephalitis |
| Urine | Urine analysis, microscopy and culture, toxicology screen | Urinary tract infection, drug toxicosis |
| Ultrasound | Bladder, kidney-ureter-bladder, echocardiography | Urinary retention, urinary tract infection, subacute bacterial endocarditis |
| X-ray | Chest, musculoskeletal | Pneumonia, heart failure, fracture |
| Neuroimaging | CT head, MRI head, DaTSCAN | Stroke, haemorrhage, structural lesions, dementia with Lewy bodies |
| Computed tomography | Chest, abdomen and pelvis | Suspecting malignancy |
| Magnetic resonance imaging | DWI, FLAIR | SOL, Alzheimer's disease, CVA |
| Lumbar puncture | CSF proteinCSF glucoseCSF TPO, M/C/SOligoclonal bandsNMDA receptor antibodiesVoltage gated calcium channel antibodiesVoltage gated potassium channel antibodiesCSF (s100, p 14-3-3) in CJD | Meningitis, encephalitis |
| Electroencephalography | Pseudo periodic triphasic complexes may be present progressive disease in prion disease (CJD) | Delirium, metabolic eg hepatic encephalopathy, epilepsy |
| DaTSCAN | Reduced ioflupane uptake | Dementia 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