Deep Cerebellar Low-Intensity Focused Ultrasound Stimulation Restores Interhemispheric Balance after Ischemic Stroke in Mice

Hongchae Baek, Anvar Sariev, Seul Lee, Suh-Yeon Dong, Sebastien Royer, Hyungmin Kim

IEEE Transactions on Neural Systems and Rehabilitation Engineering 2020, 28, 2073-2079 · 10.1109/tnsre.2020.3002207

rodentstrokeeeg megbehaviourhistology molecular

Abstract

Ischemic damage after stroke disrupts the complex balance of inhibitory and excitatory activity within cortical network causing brain functional asymmetry. Cerebellar deep nuclei with its extensive projections to cortical regions could be a prospective target for stimulation to restore inter-hemispheric balance and enhance neural plasticity after stroke. In our study, we repeatedly stimulated the lateral cerebellar nucleus (LCN) by low-intensity focused ultrasound (LIFU) for 3 days to enhance rehabilitation after middle cerebral artery occlusion (MCAO) in a mouse stroke model. The neural activity of the mice sensorimotor cortex was measured using epidural electrodes and analyzed with quantified electroencephalography (qEEG). Pairwise derived Brain Symmetry Index (pdBSI) and delta power were used to assess the neurorehabilitative effect of LIFU stimulation. Compared to the Stroke (non-treated) group, the LIFU group exhibited a decrease in cortical pathological delta activity, significant recovery in pdBSI and enhanced performance on the balance beam walking test. These results suggest that cerebellar LIFU stimulation could be a non-invasive method for stroke rehabilitation through the restoration of interhemispheric balance.

Abstract via europepmc.

Speciesmouse (ICR)

Subjects7 animals

Sessions per subject3

Randomisedyes

Blindingnot reported

Sham / controlnone

Auditory controlnot reported

Readout timingoffline

Anaesthesianot reported

Readoutseeg meg, behaviour, histology molecular — quantitative EEG (delta power, pairwise derived Brain Symmetry Index); balance beam walking test; H&E staining of cerebellum

Direction of effectinhibitoryCerebellar LIFU of the LCN reduced pathological increases in cortical delta power and restored interhemispheric symmetry (pdBSI) after stroke relative to the untreated Stroke group, and improved balance beam walking performance.

Adverse eventsnone observedThe histological assessment did not reveal any sign of damage in the cerebellum after LIFU exposure; H&E staining showed no evidence of hemorrhage, tissue damage, or Purkinje cell loss in sonicated tissue.

Exposures

Exposure 1: LIFU stimulation of lateral cerebellar nucleus (LCN)

Target: deep cerebellar nuclei — “lateral cerebellar nucleus (LCN)”
Device: Ultran · The Ultran Group · GPS350-D25_FL25 ✓

Pulse timing
Waveform	pulsed
Fundamental frequency (kHz)	350	✓✓✓
Pulse duration (ms)	0.5	✓✓✓
Pulse repetition frequency (Hz)	1,000	✓✓✓
Duty cycle (%)	50pulse duration × PRF gives 50%	✓✓✓
Sonication duration (s)	0.3	✓✓✓

Pressure and intensity, by domain
Free-field pressure (kPa)	not reported
Free-field Isppa (W/cm²)	2.56	✓✓✓
Free-field Ispta (W/cm²)	1.28	✓✓✓
In-situ estimate	not reported
In-situ pressure (kPa)	not reported
In-situ Isppa (W/cm²)	not reported
In-situ Ispta (W/cm²)	not reported

Protocol, in the paper’s words

5 s inter-stimulus interval (ISI) between 300 ms sonications; sonication applied for 20 min at acute (6 h), subacute I (24 h), and subacute II (48 h) phases only for the LIFU group, focused on the pre-marked LCN target using a customized transducer holder.

Flags from extraction

sham_type — The comparator was an untreated 'Stroke (non-treated)' group rather than a described sham-stimulation arm (no mock transducer procedure is reported), so 'none' is used but this differs from a typical inactive-transducer sham.
anaesthesia — Ketamine/xylazine anaesthesia is described for MCAO surgery and EEG baseline recording, but the paper does not clearly state whether animals were anaesthetised during the LIFU sonication sessions themselves.
n_subjects — An additional, unspecified number of mice without MCAO surgery were also sonicated for histological safety assessment; only the n=7 LIFU-treatment-group total is countable as ultrasound-exposed for the main study.