Transient splenial lesion of the corpus callosum in clinically mild influenza-associated encephalitis/encephalopathy.

BACKGROUND: Reversible lesions in the splenium of the corpus callosum (SCC), caused by various agents such as influenza, rotavirus, Escherichia coli, mumps, and adenovirus, were previously defined in a handful of cases. We present 5 cases with transient diffusion restriction of the SCC associated with influenza A virus infection. MATERIALS AND METHODS: Five patients with influenza-associated encephalitis/encephalopathy and sudden-onset neurologic symptoms following a prodromal flulike episode were examined by MR and diffusion-weighted imaging (DWI). RESULTS: Three patients, who had drowsiness and new-onset convulsions, recovered spontaneously without any medication. In the other 2 seizure-free patients, 1 had trigeminal neuralgia and headache and the other had facial numbness and left upper monoparesis. All patients had round well-defined ovoid hyperintense splenial lesions (14.94 +/- 1.87 mm) on DWI with a significantly low apparent diffusion coefficient (ADC) of 0.41 +/- 0.05 x 10(-3) mm(2)/s compared with 0.84 +/- 0.01 x 10(-3) mm(2)/s of normal-appearing white matter. In the patient with a motor deficit, additional lesions were found in the cerebral deep white matter. The high signal intensity of the splenial and deep white matter lesions on DWI completely disappeared on follow-up studies, and ADC values also improved, returning to those of normal-appearing white matter on days 8-11. Clinically, all patients completely recovered on days 4-9. CONCLUSION: A transient lesion of the SCC is a significant but nonspecific finding. It is probably due to edematous and/or inflammatory changes of the SCC. It may be the only detectable change in patients with good prognosis, indicating a clinically mild form of encephalitis/encephalopathy.

Comparison of contrast-enhanced T1-weighted and 3D constructive interference in steady state images for predicting outcome after hearing-preservation surgery for vestibular schwannoma.

We compared contrast-enhanced T1-weighted and 3D constructive interference in steady state (CISS) sequences for demonstrating possible prognostic factors in hearing-preservation surgery for vestibular schwannoma. We studied 22 patients with vestibular schwannomas having hearing-preservation surgery. Postoperatively six (27%) had a facial palsy and eight (36%) had hearing loss. There was a significant correlation between the size of the tumour and facial palsy (r=-0.72). Both techniques adequately demonstrated all tumours. Involvement of the fundus of the internal auditory canal (IAC) and a small distance between the lateral border of the tumour and the fundus were correlated significantly with hearing loss (r=-0.81 and -0.75, respectively). The 3D-CISS sequence, by virtue of its high contrast resolution was superior to T1-weighted images ( P<0.05) for detection of the fundal involvement. The direction of displacement of the facial nerve did not correlate with facial palsy or hearing loss. We think that 3D-CISS images better show the features influencing surgical outcome, but that contrast-enhanced T1-weighted images are required for diagnosis.

Diagnostic value of MRI in tuberculous meningitis.

In this study 15 patients with clinical findings and positive cerebrospinal fluid analyses for tuberculous meningitis were evaluated with magnetic resonance imaging (MRI). Tuberculous meningitis was diagnosed in 11 cases when thick meningeal enhancement was present after intravenous injection of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) in T1-weighted images. Intra-axial tuberculomas were present in 8 patients, 2 of whom had intra-axial tuberculomas without MRI evidence of meningitis. Tuberculomas showed ring or nodular enhancement in postcontrast T1-weighted images, but the most significant MR feature of intraparenchymal tuberculomas was the hypointense appearance of the lesions on T2-weighted images.