MRS in epilepsy evaluation

Sandra P. Rincon, Marisa B.K. Blitstein , Paul A. Caruso , R. Gilberto González, Ronald L. Thibert ,  Eva-Maria Ratai.  The Use of Magnetic Resonance Spectroscopy in the Evaluation of Pediatric Patients With Seizures.  Pediatric Neurology.  Published online ahead of print.

Abstract

Background

The objective was to determine if it is useful to routinely add magnetic resonance spectroscopy (MRS) to magnetic resonance imaging (MRI) in the evaluation of seizure in the pediatric patient. Specifically, how often does MRS contribute information to conventional MRI?

Methods

A retrospective search, over a period of 3 years, of patients <18 years of age who underwent both MRI and MRS as part of the evaluation of seizures yielded a total of 233 cases in 216 patients. The medical records were reviewed to determine how many patients carried a diagnosis relevant to seizures. The MRIs and MRSs were reviewed by two neuroradiologists and an MR physicist/spectroscopist who determined by consensus in how many cases MRS contributed information regarding management, diagnosis, or prognosis, in addition to the findings on MRI alone.

Results

In 100 of 233 cases (43%), MRS contributed information additional to MRI. In 40 cases, MRS contributed information relevant to patient management by prompting an evaluation for an underlying inborn error of metabolism. MRS contributed information relevant to diagnosis in 24 of 100 cases (e.g., neoplasm versus dysplasia). MRS contributed information relevant to prognosis in 36 cases (e.g., hypoxic-ischemic injury). MRS added more information in cases where the patients had a diagnosis relevant to seizure before imaging. Interestingly, in 25 cases where the MRI was normal, MRS was found to be abnormal, which prompted evaluation for an inborn error of metabolism.

Conclusions

These results suggest that MRS is a useful evaluation tool in addition to MRI for children undergoing imaging for the evaluation of seizures.

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From the manuscript

A term baby boy was delivered by C-section for failure to progress. At delivery, the baby had a weak cry and then became apneic. He was treated with positive pressure ventilation and chest compressions, and Apgar scores were 5 and 9 at 1 and 5 minutes of life, respectively. He was admitted to the newborn nursery and did well until day 3 of life when he had an episode of rigidity, “eye rolling,” and oxygen desaturation. En route to the neonatal intensive care unit, the baby had two subsequent episodes of arm stiffening, head and eye deviation, blinking, and oxygen desaturation. The patient was admitted to the neonatal intensive care unit, during which time the patient's initial MRI and MRS were obtained. Three months later, another MRI and MRS were obtained, and the patient was admitted to the Epilepsy Monitoring Unit for video-electroencephalography (EEG) monitoring.

The initial MRI findings were normal with no findings specific for HII. However, MRS placed over the left basal ganglia showed elevated lactate levels, which persisted 3 months later. Because of concerns regarding the small lactate peak on MRS, the Genetics team sent an epilepsy gene panel, which revealed several mutations, including a mutation of KCNQ2. This mutation typically results in benign neonatal seizures and has also been reported in some more difficult-to-treat epilepsies…

An 8-year-old boy presented with complaints of abnormal smells followed by fatigue. He had abnormal findings on EEG with epileptiform activity that localized to the right temporal lobe. He had abnormal findings on MRI at an outside hospital demonstrating a lesion in the right amygdala and hippocampus. This finding raised the possibility of cortical dysplasia versus neoplasm versus postictal change.

MRS findings showed elevated myoinositol-to-creatine and choline-to-NAA ratios, which were most concerning for a low-grade neoplasm.   The patient underwent subsequent surgical resection of the lesion, and pathology revealed a low-grade glioma…

Baby boy born at term via vaginal delivery, emerged limp and apneic with a double nuchal cord reduced at the perineum. Apgar scores were 1, 3, and 3 at 1, 5, and 10 minutes of life, respectively. The baby was intubated at 4 minutes of life. At 50 minutes of life, he had an episode of bilateral hand shaking lasting 30-60 seconds. On days 1-4 of life, the baby underwent therapeutic hypothermia and had an MRI on day 5 of life.

MRI findings indicate a predominantly central pattern of HII, including restricted diffusion in the bilateral globi palladi, putamina, and ventral-medial thalami. Single-voxel MRS placed over the right basal ganglia shows an elevated lactate peak. Findings were thought to be indicative of severe HII, with potentially significant prognostic implications. During the neonatal period, the deep gray matter lactate-to-NAA ratio is thought to be the most accurate quantitative MR biomarker for prediction of neurodevelopmental outcome after neonatal encephalopathy and may be useful in early clinical management decisions.