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illustration of brain showing cerebellum

Focusing on the “little brain” to rescue cognition

illustration of brain showing cerebellum

Research faculty at Children’s National in Washington, D.C., with colleagues recently published a review article in Nature Reviews Neuroscience that covers the latest research about how abnormal development of the cerebellum leads to a variety of neurodevelopmental disorders.

Cerebellum translates as “little brain” in Latin. This piece of anatomy – that appears almost separate from the rest of the brain, tucked under the two cerebral hemispheres – long has been known to play a pivotal role in voluntary motor functions, such as walking or reaching for objects, as well as involuntary ones, such as maintaining posture.

But more recently, says Aaron Sathyanesan, Ph.D., a postdoctoral research fellow at the Children’s Research Institute, the research arm of Children’s National  in Washington, D.C., researchers have discovered that the cerebellum is also critically important for a variety of non-motor functions, including cognition and emotion.

Sathyanesan, who studies this brain region in the laboratory of Vittorio Gallo, Ph.D., Chief Research Officer at Children’s National and scientific director of the Children’s Research Institute, recently published a review article with colleagues in Nature Reviews Neuroscience covering the latest research about how altered development of the cerebellum contributes to a variety of neurodevelopmental disorders.

These disorders, he explains, are marked by problems in the nervous system that arise while it’s maturing, leading to effects on emotion, learning ability, self-control, or memory, or any combination of these. They include diagnoses as diverse as intellectual disability, autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder and Down syndrome.

“One reason why the cerebellum might be critically involved in each of these disorders,” Sathyanesan says, “is because its developmental trajectory takes so long.”

Unlike other brain structures, which have relatively short windows of development spanning weeks or months, the principal cells of the cerebellum – known as Purkinje cells – start to differentiate from stem cell precursors at the beginning of the seventh gestational week, with new cells continuing to appear until babies are nearly one year old.  In contrast, cells in the neocortex, a part of the brain involved in higher-order brain functions such as cognition, sensory perception and language is mostly finished forming while fetuses are still gestating in the womb.

This long window for maturation allows the cerebellum to make connections with other regions throughout the brain, such as extensive connections with the cerebral cortex, the outer layer of the cerebrum that plays a key role in perception, attention, awareness, thought, memory, language and consciousness. It also allows ample time for things to go wrong.

“Together,” Sathyanesan says, “these two characteristics are at the root of the cerebellum’s involvement in a host of neurodevelopmental disorders.”

For example, the review article notes, researchers have discovered both structural and functional abnormalities in the cerebellums of patients with ASD. Functional magnetic resonance imaging (MRI), an imaging technique that measures activity in different parts of the brain, suggests that significant differences exist between connectivity between the cerebellum and cortex in people with ASD compared with neurotypical individuals. Differences in cerebellar connectivity are also evident in resting-state functional connectivity MRI, an imaging technique that measures brain activity in subjects when they are not performing a specific task. Some of these differences appear to involve patterns of overconnectivity to different brain regions, explains Sathyanesan; other differences suggest that the cerebellums of patients with ASD don’t have enough connections to other brain regions.

These findings could clarify research from Children’s National and elsewhere that has shown that babies born prematurely often sustain cerebellar injuries due to multiple hits, including a lack of oxygen supplied by infants’ immature lungs, he adds. Besides having a sibling with ASD, premature birth is the most prevalent risk factor for an ASD diagnosis.

The review also notes that researchers have discovered structural changes in the cerebellums of patients with Down syndrome, who tend to have smaller cerebellar volumes than neurotypical individuals. Experimental models of this trisomy recapitulate this difference, along with abnormal connectivity to the cerebral cortex and other brain regions.

Although the cerebellum is a pivotal contributor toward these conditions, Sathyanesan says, learning more about this brain region helps make it an important target for treating these neurodevelopmental disorders. For example, he says, researchers are investigating whether problems with the cerebellum and abnormal connectivity could be lessened through a non-invasive form of brain stimulation called transcranial direct current stimulation or an invasive one known as deep brain stimulation. Similarly, a variety of existing pharmaceuticals or new ones in development could modify the cerebellum’s biochemistry and, consequently, its function.

“If we can rescue the cerebellum’s normal activity in these disorders, we may be able to alleviate the problems with cognition that pervade them all,” he says.

In addition to Sathyanesan and Senior Author Gallo, Children’s National study co-authors include Joseph Scafidi, D.O., neonatal neurologist; Joy Zhou and Roy V. Sillitoe, Baylor College of Medicine; and Detlef H. Heck, of University of Tennessee Health Science Center.

Financial support for research described in this post was provided by the National Institute of Neurological Disorders and Stroke under grant numbers 5R01NS099461, R01NS089664, R01NS100874, R01NS105138 and R37NS109478; the Hamill Foundation; the Baylor College of Medicine Intellectual and Developmental Disabilities Research Center under grant number U54HD083092; the University of Tennessee Health Science Center (UTHSC) Neuroscience Institute; the UTHSC Cornet Award; the National Institute of Mental Health under grant number R01MH112143; and the District of Columbia Intellectual and Developmental Disabilities Research Center under grant number U54 HD090257.

Using fMRI for assessment prior to neurosurgery

For more than 20 years, Children’s National has explored the use of non-invasive fMRI as an alternative to more invasive testing to assess children’s language and memory.

A new Practice Guideline Summary published in Neurology, the journal of the American Academy of Neurology, contains the first complete, objective assessment of available data on the efficacy of functional magnetic resonance imaging (fMRI) to assess baseline language and memory, brain hemisphere dominance and to predict postsurgical impacts prior to surgery in patients with epilepsy.

According to contributing author William D. Gaillard, M.D., chief of Child Neurology, Epilepsy and Neurophysiology, and director of the Comprehensive Pediatric Epilepsy Program at Children’s National Health System, the report outlines several cases in which fMRI presents an effective alternative to the current standard of care, intracarotid amobarbital procedure (IAP). In IAP, medication is injected through the carotid artery to isolate one hemisphere of the brain at a time, followed by the patient performing memory or language tasks. The approach requires catheterization via a major artery. While minimally invasive, the procedure still carries the standard risks of vascular catheter procedures and requires recovery time.

“This publication took six years to complete,” Dr. Gaillard notes, “but we are happy to finally have the practice parameters that will make the case for the use of fMRI in an evidence-based way.”

Though the Practice Guidelines focus on adults, the evidence assessment included all available pediatric data as well, says Dr. Gaillard. A great deal of that data were contributed by Children’s National faculty, who lead the nation in clinical applications of fMRI. More than 20 years ago, Dr. Gaillard and his team began studying fMRI as a viable alternative to IAP to collect accurate language assessments in children, particularly those with epilepsy. Today, Children’s National is at the forefront of clinical application of fMRI, having performed about 1,000 pediatric assessments in the last two decades — more than nearly every other institution.

An 11-member panel of international experts conducted the analyses for the Practice Guidelines. Overall, the report indicates:

  • fMRI is a viable option for measuring lateralized language functions in place of IAP in medial temporal lobe epilepsy, temporal epilepsy in general or extratemporal epilepsy.
  • Evidence was insufficient to recommend fMRI over IAP for patients with temporal neocortical epilepsy or temporal tumors.
  • Pre-surgical fMRI can serve as an adequate alternative to IAP memory testing for predicting verbal memory outcome.

In closing, the authors also explicitly recommend that clinicians carefully advise every patient of the risks and benefits of both fMRI and IAP before recommending either approach.

Related resources: Use of fMRI in the presurgical evaluation of patients with epilepsy

Practice guideline summary: Use of fMRI in the presurgical evaluation of patients with epilepsy

What’s Known

Neurologists assess a patient’s baseline language and memory, and attempt to predict postsurgical impacts on language before the patient undergoes neurosurgical procedures to minimize the symptoms of epilepsy. In a standard intracarotid amobarbital procedure (IAP), a medication is injected through the carotid artery that isolates one hemisphere of the brain at a time followed by the patient performing memory tasks. More recently, neurologists have performed the assessment via functional magnetic resonance imaging (fMRI), an image acquisition technique that captures brain activity while the patient completes a set of memory and language tasks. Both approaches lack standardized implementation guidelines, making it difficult to fully assess when fMRI may be an effective alternative to IAP.

What’s New

A Practice Guideline Summary published in Neurology, the journal of the American Academy of Neurology, regarding the use of fMRI for pre-surgical evaluation of patients with epilepsy establishes recommendations related to the diagnostic accuracy of fMRI for pre-surgical evaluation. An 11-member panel of international experts, including William D. Gaillard, M.D., Chief of Child Neurology, Epilepsy and Neurophysiology, and Director of the Comprehensive Pediatric Epilepsy Program at Children’s National Health System, evaluated available evidence to determine when and if fMRI can reliably measure the extent that each brain hemisphere controls language, known as language lateralization, and as a predictor of postsurgical outcomes. For 20 years, Dr. Gaillard’s team has led the field in the application of fMRI for language and memory assessment in children, and their work comprised a large portion of the pediatric-focused research assessed by the panel. The analyses found that fMRI is a viable option for measuring lateralized language functions in place of IAP in medial temporal lobe epilepsy, temporal epilepsy in general or extratemporal epilepsy. Evidence was insufficient to recommend fMRI over IAP for patients with temporal neocortical epilepsy or temporal tumors. The assessment also identified that pre-surgical fMRI can serve as an adequate alternative to IAP memory testing for predicting verbal memory outcome. The authors recommend that clinicians carefully advise patients of the risks and benefits before recommending either approach.

Questions for Future Research

Q: What is role of fMRI for pediatric epilepsy?
Q: Can a standard set of tasks be established as the guideline for assessment?

Source: J.P. Szaflarski, D. Gloss, J.R. Binder, W.D. Gaillard, A.J. Golby, S.K. Holland, J. Ojemann, D.C. Spencer, S.J. Swanson, J.A. French and W.H.Theodore. “Practice Guideline Summary: Use of fMRI in the Presurgical Evaluation of Patients With Epilepsy.” Published by Neurology in January 2017.