Neuroimaging Studies of Stroke Rehabilitation

OR: Why is the RSNA Makin' Stuff Up? (Part 2)

Here's the next erroneous press release from the Radiological Society of North America (RSNA):

Robotic Technology Improves Stroke Rehabilitation

CHICAGO — esearch [sic] scientists using a novel, hand-operated robotic device and functional MRI (fMRI) have found that chronic stroke patients can be rehabilitated, according to a study presented today at the annual meeting of the Radiological Society of North America (RSNA). This is the first study using fMRI to map the brain in order to track stroke rehabilitation.

No, not even close. Many published papers have used fMRI to map the brain in order to track stroke rehabilitation. Three recent review articles are listed in the References.

"We have shown that the brain has the ability to regain function through rehabilitative exercises following a stroke," said A. Aria Tzika, Ph.D., director of the NMR Surgical Laboratory at Massachusetts General Hospital (MGH) and Shriners Burn Institute and assistant professor in the Department of Surgery at Harvard Medical School in Boston. "We have learned that the brain is malleable, even six months or more after a stroke, which is a longer period of time than previously thought."

That's not true, either, because the literature on post-stroke recovery of function includes articles like the one by Liepert et al. (back in 2000) on constraint-induced movement therapy in patients with strokes 5 years earlier:

...CI therapy might produce its therapeutic effect through the induction of a use-dependent cortical reorganization that counteracts adverse brain function changes and enhances recovery-associated plastic changes that occur in the human brain after stroke.

Well, the robotic technology is cool, let's take a look at that.

For the study, the patients squeezed a special MR-compatible robotic device for an hour a day, three days per week for four weeks. fMRI exams were performed before, during, upon completion of training and after a non-training period to assess permanence of rehabilitation.

Figure 4 (Tzika et al., 2008). Diagram illustrating the concept of on-line brain mapping using fMRI and a Magnetic Resonance Compatible Hand-Induced Robotic Device (MR_CHIROD).

The intensive rehabilitation regime produced an increase in the number of voxels activated when the patients were using MR_CHIROD in the scanner.


Figure 16 (Tzika et al., 2008). This fMRI image illustrates the area in the brain that corresponds with hand use of a patient before training (left), after eight weeks of training (middle), and one month after training was completed (right) at a 60percent effort level.

Earlier experiments have reported similar findings (e.g., Dong et al., 2007). In fact, the excellent review paper by Carey and Seitz (2007), which has 244 references, includes a table of 12 neuroimaging studies that specifically looked at rehabilitation of the upper limb in stroke patients.

So to conclude, this is not the first time fMRI has been used to track rehabilitation, and it's not news that the potential for cortical plasticity persists at six or more months post-stroke. Why would a professional society release false PR to promote their annual meeting?


References

1. Reviews

Carey LM, Seitz RJ. (2007). Functional neuroimaging in stroke recovery and neurorehabilitation: conceptual issues and perspectives. Int J Stroke 2:245-64.

Eliassen JC, Boespflug EL, Lamy M, Allendorfer J, Chu WJ, Szaflarski JP. (2008). Brain-mapping techniques for evaluating poststroke recovery and rehabilitation: a review. Top Stroke Rehabil. 15:427-50.

Brain-mapping techniques have proven to be vital in understanding the molecular, cellular, and functional mechanisms of recovery after stroke. This article briefly summarizes the current molecular and functional concepts of stroke recovery and addresses how various neuroimaging techniques can be used to observe these changes. The authors provide an overview of various techniques including DTI, MRS, ligand-based PET, SPECT, rCBF and rCMRglc PET and SPECT, fMRI, NIRS, EEG, MEG, and TMS. Discussion in the context of poststroke recovery research informs about the applications and limitations of the techniques in the area of rehabilitation research. The authors also provide suggestions on using these techniques in tandem to more thoroughly address the outstanding questions in the field.

Ward NS. (2007). Future perspectives in functional neuroimaging in stroke recovery. Eura Medicophys. 43:285-94.

Neurological damage and stroke in particular is the leading cause of long-term disability worldwide. Recovery of function after stroke is a consequence of many factors including resolution of oedema and survival of the ischaemic penumbra. In addition, there is a growing interest in how reorganisation of the surviving tissue might subserve the improvements in function that are commonly seen over weeks, months, and sometimes years after stroke. Noninvasive techniques such as functional magnetic resonance imaging, electroencephalography, magnetoencephalography and transcranial magnetic stimulation allow the study of this reorganisation in humans. Currently, results suggest that functionally relevant reorganisation does occur in cerebral networks in human stroke patients. This reorganisation can only occur in structurally and functionally intact brain regions. Because these vary depending on the location of the infarction, it is likely that different therapeutic strategies will be required to promote reorganisation depending on residual functional anatomy. This review maps out the attempts to describe functionally relevant adaptive changes in the human brain following focal damage. A greater understanding of how these changes are related to the recovery process will facilitate the development of novel therapeutic techniques designed to minimise impairment based on neurobiological principles and how to target these treatments to individual patients.

2. Primary articles

Dong Y, Winstein CJ, Albistegui-DuBois R, Dobkin BH. (2007). Evolution of FMRI activation in the perilesional primary motor cortex and cerebellum with rehabilitation training-related motor gains after stroke: a pilot study. Neurorehabil Neural Repair. 21:412-28.

Liepert J, Bauder H, Wolfgang HR, Miltner WH, Taub E, Weiller C. (2000). Treatment-induced cortical reorganization after stroke in humans. Stroke 31:1210-6.

BACKGROUND AND PURPOSE: Injury-induced cortical reorganization is a widely recognized phenomenon. In contrast, there is almost no information on treatment-induced plastic changes in the human brain. The aim of the present study was to evaluate reorganization in the motor cortex of stroke patients that was induced with an efficacious rehabilitation treatment. METHODS: We used focal transcranial magnetic stimulation to map the cortical motor output area of a hand muscle on both sides in 13 stroke patients in the chronic stage of their illness before and after a 12-day-period of constraint-induced movement therapy. RESULTS: Before treatment, the cortical representation area of the affected hand muscle was significantly smaller than the contralateral side. After treatment, the muscle output area size in the affected hemisphere was significantly enlarged, corresponding to a greatly improved motor performance of the paretic limb. Shifts of the center of the output map in the affected hemisphere suggested the recruitment of adjacent brain areas. In follow-up examinations up to 6 months after treatment, motor performance remained at a high level, whereas the cortical area sizes in the 2 hemispheres became almost identical, representing a return of the balance of excitability between the 2 hemispheres toward a normal condition. CONCLUSIONS: This is the first demonstration in humans of a long-term alteration in brain function associated with a therapy-induced improvement in the rehabilitation of movement after neurological injury.