Challenges in Identifying the Foot Motor Region in Patients with Brain Tumor on Routine MRI: Advantages of fMRI

Vagus Nerve Stimulation Paired With Mobility Training in Chronic Ischemic Stroke: A Case Report

OBJECTIVE

The purpose of this case report is to describe pairing vagus nerve stimulation (VNS) with mobility training in an individual after stroke.

METHODS

A 53-year-old man with left hemiparesis 14.2 months after an ischemic stroke participated in a pilot study investigating the safety and feasibility of VNS paired with upper limb rehabilitation. In addition to upper limb impairment, the participant had impaired gait and wanted to improve his mobility. A single-subject design investigation of VNS paired with self-directed mobility training was conducted. Following the conclusion of the pilot study, the participant was instructed to complete daily sessions of self-activated VNS paired with walking or stationary biking. The 10-Meter Walk Test and timed distance (6-Minute Walk Test) were assessed at 4 baseline points and at 3 to 41 months after mobility training.

RESULTS

The participant had stable baseline values and was classified as a household ambulator with a quad cane. After VNS-paired mobility training, statistically significant improvements were observed in all measures, with the greatest improvements at 9 months exceeding the minimal detectable change: self-selected gait speed from 0.34 (standard deviation [SD] = 0.01) to 0.60 meters/second, fast gait speed from 0.37 (SD = 0.03) to 0.79 meters/second, and 6-Minute Walk Test distance from 106.91 (SD = 6.38) to 179.83 meters. The participant reported increased confidence and balance when walking. No falls or adverse events were reported.

CONCLUSION

The participant demonstrated improved gait speed and timed distance after VNS-paired mobility training. Randomized, blinded trials are needed to determine treatment efficacy.

IMPACT

This is the first documented case of VNS-paired mobility training in an individual with chronic poststroke gait impairments. VNS paired with mobility training may improve poststroke gait impairments.

Anatomical and neurophysiological localization of the leg motor area at the medial central sulcus

OBJECTIVE

The exact location of the leg motor area is still in debate due to the lack of landmarks such as 'precentral knob' in the medial cortex. This study tried to identify the leg motor area based on intraoperative neurophysiological data and neuroimaging techniques.

METHODS

Intraoperative data of somatosensory evoked potential (SEP) elicited by tibial nerve stimulation and motor evoked potential (MEP) of the leg muscles induced by direct cortical stimulation were recorded using subdural electrodes placed in the medial cortex. We displayed the neurophysiological data on the individual MR images and the MNI52.

RESULTS

Definite N40-P40 phase reversal was observed with the shallow grooves in the medial cortex in 5 cases. Leg MEP was successfully obtained in all 12 cases preserving the leg motor function. Superimposed SEP and leg MEP data on the MNI152 indicated the leg motor area was predominantly located in the posterior two-thirds between the vertical lines passing through the anterior commissure and the posterior commissure (VCP).

CONCLUSIONS

Our study revealed the location of the leg motor area and the presence of the 'medial central sulcus' in the medial cortex.

SIGNIFICANCE

The VCP can be useful landmark to identify the sensorimotor border in the medial cortex.

Functional Brain Anatomy

Knowledge of functional neuroanatomy is essential to design the most appropriate clinical functional MR imaging (fMR imaging) paradigms and to properly interpret fMR imaging study results. The correlation between neuroanatomy and brain function is also useful in general radiologic practice, as it improves the radiologist's ability to read routine brain examinations. Functional MR imaging is used primarily to determine the areas involved in functioning of movements, speech, and vision. Preoperative fMR imaging findings also play a key role in the neurosurgeon's decision to perform a biopsy, a subtotal resection, or a maximal resection using awake craniotomy.