Anti-N-methyl-D-aspartate receptor-associated encephalitis: A review of clinicopathologic hallmarks and multimodal imaging manifestations

Table 3 Multimodal imaging of anti-N-methyl-D-aspartate receptor-associated encephalitis[12-24]

Ultrasound	Pelvic or scrotal ultrasound may be used to identify an underlying teratoma in the appropriate patient population
	Ultrasound-guided lymph node biopsy may be required in the setting of metastatic disease with no known primary
MRI	A normal brain MRI is present in half of patients with NMDARE
	T2/FLAIR hyperintense lesions are most commonly present within the supratentorial brain parenchyma and may correlate with prognosis:
	Type 1: Normal brain MRI; favorable prognosis
	Type 2: Hippocampal lesions only; poor prognosis
	Type 3: Lesions involving structures other than the hippocampus; intermediate prognosis
	Type 4: Lesions involving both the hippocampus and other brain structures; poor prognosis
	Infratentorial, spinal cord, and cranial nerve lesions are less common, but may occur in some individuals
	Leptomeningeal enhancement is rare, but has been described
MRS	Reduced NAA peak
	Decreased NAA/creatine ratio
	Increased choline peak
FDG PET	Brain FDG PET classically shows bifrontal hypermetabolism with parieto-occipital hypometabolism
	The frontal-to-parietooccipital metabolic gradient may correlate with prognosis, with an increased gradient portending a worse outcome
	Whole-body FDG PET may be of value to identify a primary neoplasm and/or localize a lesion for image-guided biopsy
SPECT	HMPAO and I-123-IMP SPECT may be useful for metabolic evaluation in patients with clinical features of NMDARE and a normal brain MRI and FDG PET

FDG PET: Fludeoxyglucose positron emission tomography; HMPAO: Technetium-99 hexamethyl propylenamine oxamine; I-123-IMP: N-isopropyl-p-123-I-iodoamphetamine; MRI: Magnetic resonance imaging; MRS: Magnetic resonance spectroscopy; NAA: N-acetylaspartate; NMDARE: Anti-N-methyl-D-aspartate receptor-associated encephalitis; SPECT: Single-photon emission computed tomography.