Table 1

Investigations to exclude secondary causes of parkinsonism in atypical cases28 40

Blood testsSerum electrolytes, caeruloplasmin, thyroid function tests, parathyroid hormone, blood film, HIV and syphilis serology, autoantibodies (NMDAR, LGI1, CRMP5, Ri, DPPX, Ma2)Wilson disease, hyper and hypothyroidism, hypoparathyroidism and pseudohypoparathyroidism, neuroacanthocytosis, HIV and neurosyphilis, autoimmune encephalitis
Urine24 hour urine copperWilson disease
CSFViral PCR, syphilis, autoantibodies, 14-3-3Encephalitis, neurosyphilis, autoimmune encephalitis, prion disease
ImagingMRI brainStructural brain lesions (normal pressure hydrocephalus, chronic subdural haematoma, tumours), stroke, evidence of previous head trauma, encephalitis, manganese intoxication, specific atrophy patterns in atypical parkinsonian syndromes, for example midbrain predominant atrophy in PSP
CT brainCalcium deposition in the basal ganglia (Fahr disease)
Genetic testingDCTN1Perry syndrome
ATP13A2Kufor-Rakeb syndrome
FMR1Fragile X-associated tremor/ataxia syndrome
HTTHuntington’s disease with parkinsonism
CSF1RAdult-onset leukoencephalopathy with axonal spheroids and pigmented glia
POLGMitochondrial disorder with parkinsonism
GBAGaucher’s disease
NPC1 and NPC2Niemann-Pick C disease
CYP27A1Cerebrotendinous xanthomatosis
  • anti-Ri, anti-neuronal nuclear antibody type 2; ATP13A2, Gene, locus PARK9; CRMP5, collapsin response-mediating protein 5; CSF, cerebrospinal fluid; CSF1R, colony stimulating factor 1 receptor; CT, computed tomography; CYP27A1, cytochrome P450 family 27 subfamily A member 1; DCTN1, Gene encoding the dynactin subunit p150; DPPX, dipeptidyl-peptidase-like protein 6; FMR1, fragile x mental retardation 1; GBA, glucosidase beta acid; HIV, human immunodeficiency virus; HTT, Huntingtin gene; LGI1, leucine-rich glioma inactivated 1; Ma2, anti-Ma2; MRI, magnetic resonance imaging; NMDAR, N-methyl-D-aspartate receptor; NPC1, Niemann-Pick disease, type C1; NPC2, Niemann-Pick disease, type C2; PCR, polymerase chain reaction; POLG, DNA polymerase gamma gene; PSP, progressive supranuclear palsy.