MR Imaging of Human Herpesvirus-6 Encephalopathy after Hematopoietic Stem Cell Transplantation in Adults

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Fig 1.
Axial MR images of an HHV-6 encephalopathy patient (patient 2) obtained on the second day after the onset of neurologic symptoms.
A, T1WI (TR/TE = 466/11 ms).
B, T2WI (2650/93 ms).
C, FLAIR (TR/TE/TI = 9000/97/2300 ms).
D, DWI (TR/TE = 3100/119 ms, b = 1000).
E, ADC map.
F, postcontrast T1WI (TR/TE = 558/17 ms).
An abnormal low signal intensity on T1WI (A) and high signal intensity on T2WI (B) and FLAIR (C) are shown in the bilateral amygdalae and hippocampi. High signal intensity on DWI (D) with ADC reduction (E) is also shown. However, no abnormal enhancement is seen on postcontrast T1WI (F).
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Fig 2.
Serial axial MR images of a 49-year-old woman (patient 1) including FLAIR (TR/TE/TI = 9000/110/2200 ms [A, B, D] or 9000/97/2300 ms [C]), DWI (TR/TE = 4000/137 ms [E, F, H] or 3100/119 ms [G]), and ADC maps on days 1, 13, 26, and 98 after the onset of neurologic symptoms (I-L). On FLAIR, high signal intensity in the bilateral amygdalae and hippocampi appears on day 1, peaks on day 13, and becomes less pronounced on day 26, disappearing on day 98 but leaving marked atrophy. High signal intensity on DWI is observed until day 26, whereas ADC value reduction is seen only on days 1 and 13.

Table 1:

Summary of patient histories

Patient no: Age/Sex	Primary Disorder	Type of Transplant	Interval between Transplantation and Symptoms Onset	Neurological Symptoms					Specimen and Quantity of HHV-6 PCR	Outcome
Patient no: Age/Sex	Primary Disorder	Type of Transplant	Interval between Transplantation and Symptoms Onset	Disorientation	Short-term Memory Loss	Coma	Hypopnea	Convulsion	Specimen and Quantity of HHV-6 PCR	Outcome
1:49/F	Acute leukemia	Cord blood stem cell	27	+	+				9000 (CSF) and 3000 (blood^*) copies/mL	Improved (remaining disorientation and memory loss)
2:41/F	Acute leukemia	(Peripheral blood stem cell)	(979)		+	+			49,000 copies/mL (CSF)	Improved (remaining disorientation and memory loss)
3:55/M	Non-Hodgkin lymphoma	Bone marrow	22	+			+		400,000 copies/mL (blood)	Dead (sepsis)
4:52/M	Non-Hodgkin lymphoma	Bone marrow	14	+	+			+	58,000 copies/mL (CSF)	Improved
5:36/M	Acute leukemia	Bone marrow	19	+	+	+	+	+	2300 copies/mL (CSF)	Dead (intestinal pneumonitis)
6:37/F	Acute leukemia	Bone marrow	17			+	+	+	3000 copies/mL (CSF)	Dead (liver failure)

Table 2:

MR findings in the amygdala/hippocampus and the time interval from the onset of neurological symptoms

Time of Imaging with Reference to Symptom Onset		Imaging Findings in the Amygdala/Hippocampus
	Plain CT	T1WI	T2WI	FLAIR	DWI	ADC Value	Gd-T1WI	Others on MR
	Abnormal findings	Low	High	High	High	Reduction	Abnormal enhancement	Atophic change
Early period, days 1–2 (n = 4 patients)	0/3 (0%)	2/4 (50%)	2/4 (50%)	2/3 (67%)	2/2 (100%)	2/2 (100%)	0/2 (0%)	0/4 (0%)
Middle period, days 3–30 (n = 4 patients)		5/6 (83%)	4/6 (67%)	5/6 (83%)	3/5 (60%)	1/3 (33%)	0/2 (0%)	2/6 (33%)
Late period, days 31+ (n = 4 patients)		0/4 (0%)	0/4 (0%)	0/4 (0%)	0/4 (0%)	0/2 (0%)	0/2 (0%)	4/4 (100%)

Note:—Gd-T1WI indicates gadolinium-diethylene triaminepentaacetic acid T1-weighted imaging; ADC, apparent diffusion coefficient; T1WI, T1-weighted imaging; T2WI, T2-weighted imaging; FLAIR, fluid-attenuated inversion recovery; DWI, diffusion-weighted imaging.

Table 3:

ADC ratio of abnormal to normal brain parenchyma

Time of Imaging with Reference to Symptom Onset	Patients No.: Age/Sex
Time of Imaging with Reference to Symptom Onset	1:49/F	2:41/F	3:55/M
Early period, days 0–2 (n = 2 patients)	59% (day 1)	77% (day 2)
Middle period, days 3–30 (n = 3 patients)	83% (day 13)	100% (day 22)	114% (day 12)
	89% (day 26)
Late period, days 31+ (n = 2 patients)	137% (day 47)	132% (day 45)
	115% (day 98)