Reperfusion phenomenon masking acute and subacute infarcts at dynamic perfusion CT: confirmation by fusion of CT and diffusion-weighted MR images.

OBJECTIVE: The purpose of this study was to evaluate cerebral blood flow, cerebral blood volume, mean transit time, time to peak, and delay in a selected sample of patients with visually normal or increased cerebral blood volume to facilitate detection of a postischemic CT perfusion hyperperfusion-reperfusion phenomenon that may mask subacute and acute infarcts. MATERIALS AND METHODS: Ten patients were included who had visually normal or elevated cerebral blood volume in infarcts larger than 1.5 cm confirmed on diffusion-weighted MR images within 48 hours of perfusion CT. The cases were selected from 371 perfusion CT studies of stroke patients (99 associated with positive diffusion-weighted imaging findings) reviewed over 2.5 years on a 64-MDCT scanner. The perfusion CT images were fused to the diffusion-weighted images for measurement of cerebral blood volume, cerebral blood flow, mean transit time, time to peak, and delay in each infarct versus the contralateral hemisphere. Two neuroradiologists reviewed the images in consensus. RESULTS: The mean time between symptom onset and perfusion CT was 3.9 days. Infarcts were in the middle cerebral artery (n = 7) and posterior cerebral artery (n = 3) distributions. Significant differences versus the contralateral finding were found in cerebral blood volume (p = 0.016; mean increase, 30.0%), mean transit time (p = 0.007; mean increase, 38.1%), time to peak (p = 0.005; mean increase, 17.7%), and delay (p = 0.030; mean increase, 124.9%). The difference in cerebral blood flow (p = 0.785; mean increase, 1.8%) was not statistically significant. Infarcts became enhanced on the dynamic perfusion CT images of eight of 10 patients and on the contrast-enhanced T1-weighted MR images of six of nine patients. CONCLUSION: Visual inspection of cerebral blood volume and cerebral blood flow maps alone is insufficient in the evaluation of infarcts. Mean transit time, time to peak, and delay maps also should be reviewed with dynamic source images to prevent misinterpretation of findings as false-negative. This phenomenon is unlikely to occur hyperacutely (< 8 hours after onset).

Unilateral hypoxic-ischemic injury in young children from abusive head trauma, lacking craniocervical vascular dissection or cord injury.

BACKGROUND: Abusive head trauma (AHT) in young children usually has a severe outcome when associated with hypoxic-ischemic encephalopathy (HIE), which is best characterized by MRI in the acute or subacute phase utilizing diffusion-weighted imaging (DWI). HIE in this setting has been hypothesized to result from stretching of the spinal cord, brainstem, or vasculature. OBJECTIVE: To provide clinical correlation in patients with unilateral HIE and to postulate a mechanism in the setting of suspected AHT. MATERIALS AND METHODS: IRB approval was obtained. Over a 5-year period, the medical records and images were reviewed of the 53 children < or = 3 years of age who presented with acute head trauma according to the hospital registry. The children were subselected in order to determine how many suffered either HIE or AHT, and to detect those with unilateral HIE. RESULTS: In 11 of the 53 children, the etiology of the head trauma was highly suspicious for abuse. In 38 the head trauma was accidental and in 4 the trauma was of unknown etiology and at the time of this report was unresolved legally. Of the 53, 4 suffered HIE confirmed by CT or MRI. In three of these four with HIE the trauma was considered highly suspicious for AHT. Two of these three were the only patients with unilateral HIE, and both (7 months and 14 months of age) presented with early subacute phase HIE seen on DW MRI (range 4-7 days) and are described in detail with clinical correlation. The third child with AHT and HIE had bilateral findings. In the fourth patient the HIE was bilateral and was considered accidental. The work-up for both patients with unilateral HIE included head CT, craniocervical MRI, and craniocervical MR angiography (MRA). In both, there was mostly unilateral, deep white matter restricted diffusion, with subdural hematomas that were small compared to the extent of hypoxic-ischemic insult, and no skull fracture. Craniocervical MRA and axial thin-section fat-saturation images were negative for dissection, brainstem, or cord injury. Legal authorities obtained a confession of inflicted injury in one and a partial confession in the second (which did not fit the extent of injury). Five other children with HIE (based on DWI) were found during this period who had not suffered head trauma; all were bilateral insults. CONCLUSION: HIE associated with AHT might present with largely unilateral white matter injury on DWI following extensive cortical infarction. We propose that unilateral HIE in a young child might be a sign of AHT and might result from cervical vascular compression, whether from kinking during hyperflexion/hyperextension or from direct strangulation.

MR imaging of a ruptured intraspinal dermoid tumour with fat droplets in the central spinal canal.

We report a patient with intramedullary ruptured spinal dermoid tumour. The MR imaging revealed an intra-medullary lumbar mass heterogenous in intensity in all sequences. Fat droplets were observed in the subarachnoid space as well as in the dilated central spinal canal. Fat droplets in the subarachnoid space are frequently seen in the rupture of intraspinal dermoid tumours; however, fat droplets within the central canal is quite rare and was unexpected. Magnetic resonance imaging is a useful tool in the determination of spinal pathologies before they become large enough to cause severe symptoms and/or morbidity.

Stent angioplasty of closed mesocaval shunt in a patient with Budd-Chiari syndrome.

Budd-Chiari syndrome (BCS) is an uncommon disorder caused by hepatic venous outflow obstruction. It is characterized by ascites, hepatomegaly and abdominal pain. Percutaneous interventions have recently been used for the treatment of BCS. We present a case of BCS with a closed mesocaval shunt which was reopened with a self-expandable metallic stent.

Trigeminal nerve involvement in T-cell acute lymphoblastic leukemia: value of MR imaging.

A 30-year-old male with T-cell acute lymphoblastic leukemia presented with facial numbness. Neurological examination revealed paresthesia of the left trigeminal nerve. Cerebrospinal fluid (CSF) cytology showed no atypical cells. Gadolinium-enhanced magnetic resonance (MR) imaging demonstrated enlargement and enhancement of intracranial portions of the left trigeminal nerve. The abnormal MR imaging findings almost completely resolved after the chemotherapy. Gadolinium-enhanced MR imaging is not only a useful procedure for the early diagnosis of cranial nerve invasion by leukemia but it might be helpful to follow the changes after the treatment.