Table 1.

Results of Laboratory Tests.

HD	Study	Sample origin	Result	Notes
Autoimmune/paraneoplastic studies
2	Mayo encephalopathy/autoimmune evaluation	Serum	Negative
2	Mayo encephalopathy/autoimmune evaluation	CSF	Negative	Additionally negative on HD18, 31
2	ANA	Serum	Negative	Additionally negative on HD16
2	ANCA	Serum	Negative
2	Oligoclonal banding	Serum	Negative	Additionally negative on HD18
2	Oligoclonal banding	CSF	Negative	Additionally negative on HD18, 31
15	Thyroperoxidase antibody	Serum	Negative
15	Antithyroglobulin	Serum	Negative
16	Mayo encephalopathy/autoimmune evaluation	Serum	Positive for N‐type calcium channel antibody 1
16	SSA antibody	Serum	Negative
16	SSB antibody	Serum	Negative
16	Smith antibody	Serum	Negative
16	RNP antibody	Serum	Negative
16	Anti‐DNA (double stranded) antibody	Serum	Negative
18	Mayo Paraneoplastic/Autoantibody Evaluation	CSF	Negative	Additionally negative on HD31
30	Voltage‐Gated Potassium Channel Antibody	Serum	Negative
30	Mayo Encephalopathy/Autoimmune Evaluation	Serum	Positive for GAD65 Antibody and N‐type Calcium Channel Antibody 1
Metabolic studies
1	TSH	Serum	Within normal limits
2	Free T4	Serum	Within normal limits
10	TSH	Serum	Within normal limits
Neoplastic studies
2	CSF flow cytometry	CSF	No evidence of immunophenotypic abnormalities
2	CSF cytology	CSF	Negative for malignant cells
3	Neuron‐specific enolase	Serum	Negative
31	Flow cytometry, peripheral blood	Blood	Within normal limits
Infectious studies
1	COVID‐19 PCR	Nasopharyngeal	Negative	Additionally negative on HD15, 25
2	Ehrlichia/anaplasma PCR	Serum	Negative
2	West Nile virus PCR	CSF	Negative
2	Enterovirus PCR	CSF	Negative
2	Eastern equine encephalitis IgG, IgM	CSF	Negative	Additionally negative on HD18
2	Epstein–Barr virus, IgM	Serum	Equivocal
2	Epstein–Barr virus, IgG	Serum	Positive
2	Varicella Zoster virus PCR	CSF	Negative	Additionally negative on HD18
2	Herpes simplex virus 1/2 PCR	CSF	Negative	Additionally negative on HD18
2	Cryptococcal antigen	CSF	Negative
2	Lyme IgG	CSF	Negative
2	VDRL	CSF	Negative
17	HIV 1/2 antigen and antibody	Serum	Negative
31	RT‐QuIC for sporadic Creutzfeldt–Jakob disease	CSF	Negative
Toxicology studies
1	Toxicology screen	Urine	Positive for benzodiazepines	Had been treated with lorazepam

Table of notable autoimmune, paraneoplastic, metabolic, neoplastic, and infectious studies that were conducted. CSF, cerebrospinal fluid. HD, hospital day.

¹Note that positive serum tests for GAD65 and N‐type calcium channel antibody were considered false positives in the setting of prior IVIG administration.