DTI fiber tracking to differentiate demyelinating diseases from diffuse brain stem glioma.

OBJECT: Intrinsic diffuse brainstem tumors and demyelinating diseases primarily affecting the brainstem can share common clinical and radiological features, sometimes making the diagnosis difficult especially at the time of first clinical presentation. To explore the potential usefulness of new MRI sequences in particular diffusion tensor imaging fiber tracking in differentiating these two pathological entities, we review a series of brainstem tumors and demyelinating diseases treated at our institution. MATERIAL AND METHODS: The clinical history including signs and symptoms and MRI findings of three consecutive demyelinating diseases involving the brainstem that presented with diagnostic uncertainty and three diffuse intrinsic brainstem tumors were reviewed, along with a child with a supratentorial tumor for comparison. Fiber tracking of the pyramidal tracts was performed for each patient using a DTI study at the time of presentation. Additionally Fractional Anisotropy values were calculated for each patient in the pons and the medulla oblongata. RESULTS: Routine MR imaging was unhelpful in differentiating between intrinsic tumor and demyelination. In contrast, retrospective DTI fiber tracking clearly differentiated the pathology showing deflection of the pyramidal tracts posteriorly and laterally in the case of intrinsic brainstem tumors and, in the case of demyelinating disease, poorly represented and truncated fibers. Regionalized FA values were variable and of themselves were not predictive either pathology. CONCLUSION: DTI fiber tracking of the pyramid tracts in patients with suspected intrinsic brainstem tumor or demyelinating disease presents two clearly different patterns that may help in differentiating between these two pathologies when conventional MRI and clinical data are inconclusive.

Cerebral MRI abnormalities associated with vigabatrin therapy.

PURPOSE: Investigate whether patients on vigabatrin demonstrated new-onset and reversible T(2)-weighted magnetic resonance imaging (MRI) abnormalities. METHODS: MRI of patients treated during vigabatrin therapy was reviewed, following detection of new basal ganglia, thalamus, and corpus callosum hyperintensities in an infant treated for infantile spasms. Patients were assessed for age at time of MRI, diagnosis, duration, and dose, MRI findings pre-, on, and postvigabatrin, concomitant medications, and clinical correlation. These findings were compared to MRI in patients with infantile spasms who did not receive vigabatrin. RESULTS: Twenty-three patients were identified as having MRI during the course of vigabatrin therapy. After excluding the index case, we detected new and reversible basal ganglia, thalamic, brainstem, or dentate nucleus abnormalities in 7 of 22 (32%) patients treated with vigabatrin. All findings were reversible following discontinuation of therapy. Diffusion-weighted imaging (DWI) was positive with apparent diffusion coefficient (ADC) maps demonstrating restricted diffusion. Affected versus unaffected patients, respectively, had a median age of 11 months versus 5 years, therapy duration 3 months versus 12 months, and dosage 170 mg/kg/day versus 87 mg/kg/day. All affected patients were treated for infantile spasms; none of 56 patients with infantile spasms who were not treated with vigabatrin showed the same abnormalities. DISCUSSION: MRI abnormalities attributable to vigabatrin, characterized by new-onset and reversible T(2)-weighted hyperintensities and restricted diffusion in thalami, globus pallidus, dentate nuclei, brainstem, or corpus callosum were identified in 8 of 23 patients. Young age and relatively high dose appear to be risk factors.

Elevated cerebral blood flow velocities in Fabry disease with reversal after enzyme replacement.

BACKGROUND AND PURPOSE: Fabry disease is an X-linked inherited disorder resulting from a deficiency of alpha-galactosidase A. Cerebrovascular disease in Fabry disease includes small-vessel disease and larger-vessel ectasia in a predominantly posterior distribution. We assessed transcranial Doppler (TCD) blood flow velocities in naive and enzyme-treated Fabry patients. METHODS: TCD was used to noninvasively examine patients with Fabry disease for abnormal cerebral blood flow velocities. TCD measurements were also made during CO2 retention by breathholding to examine cerebrovascular vessel reactivity. Twenty-six patients were enrolled in a 6-month, double-blind, placebo-controlled trial of enzyme replacement therapy consisting of biweekly intravenous alpha-galactosidase A infusions, with a subsequent 18-month follow-up in an open-label trial. Statistical analysis consisted of applying a mixed-effects ANOVA model for correlated outcomes. RESULTS: Peak velocity, mean velocity, pulsatility index, and resistance index were found to be significantly higher in patients compared with control subjects. When the individual vessels were considered, elevated flow velocities were found in the middle cerebral M1 branch and the posterior cerebral artery. Enzyme replacement therapy significantly decreased peak, mean, and end-diastolic velocities and flow acceleration at the 18-month follow-up time point. CONCLUSIONS: Patients with Fabry disease have elevated cerebral blood flow velocities. These velocities significantly improved with enzyme replacement therapy.