MR spectroscopy may assist stroke assessment

MR spectroscopy (MRS) may help assess patients with acute ischemic stroke, and may provide additional metabolic information, according to a study published in the December issue of Stroke.

Recent stroke developments have focused on identifying potentially salvageable tissue—the ischemic penumbra. MRS, which has not been integrated into MR stroke protocols, may provide a means to identify the ischemic penumbra, according to Krishna A. Dani, MRCP, PhD, from the National Institute of Neurological Disorders and Stroke in Bethesda, Md., and colleagues.

Dani and colleagues designed a retrospective study to evaluate metabolite changes within tissue compartments and assess whether MRS can provide useful data. The study population was comprised of 32 patients who underwent MRS as part of the routine 3T MR stroke protocol between October 2008 and January 2010.

The MRS dataset included 136 voxels, and 128 were fully analyzed. A total of 111 voxels completely or mostly covered the diffusion-weighted imaging (DWI) lesions, and 66 of these were completely or mostly hypoperfused. “Six voxels covered hypoperfused regions with no DWI lesion, and 11 voxels covered hypoperfused voxels, which were partially (<50 percent) affected by DWI lesion, in a ‘reverse mismatch’ pattern,” wrote Dani et al.

A perfusion-weighted imaging (PWI)-DWI mismatch was present on 17 voxels in eight patients. In six voxels, lactate was detectable in significant concentrations.

Lactate preceded the appearance of the lesions on DWI imaging in some voxels and lagged behind it in others, according to the researchers. Current MRI parameters predicted up to 41 percent of the variance observed in MRS metabolites, they continued.

MRS might help characterize penumbral definition by PWI-DWI mismatch, according to Dani and colleagues. Considering lactate in addition to the mismatch region could help determine the ischemic penumbra. However, testing this theory requires a study of a large number of patients with mismatch at baseline.

The researchers noted that the study confirmed the value of current MRI protocols, and demonstrated the utility of time to maximum of the residual function as a marker of metabolic activity. The study also suggested that combination of radiological parameters and serum glucose concentration is powerful for the prediction of tissue viability, according to Dani and colleagues.

“MRS may therefore be a reliable tool for the investigation of the pathophysiology of stroke,” Dani et al concluded. However, they confirmed it may be difficult to introduce as part of the routine stroke protocol.