SMA-like syndrome without SMA lesion: Patterns of structural and functional disconnection in a relapsing low grade glioma

Introduction

Supplementary Motor Area syndrome (SMAs), a severe but transient syndrome inducing contralateral akinesia and language deficits, typically arises from lesion involving the Supplementary Motor Area (SMA). Through a functional and structural disconnection approach, we investigated whether lesion-related neuropsychological symptoms could be explained in terms of hodotopical loss of integrity across the whole-brain connectome.

Method

We report a case of a 53-year-old man who underwent resection of the left lateral inferior frontal gyrus, as well as the middle and superior frontal gyri for a low-grade glioma recurrence. Although without SMA lesion, he developed SMA syndrome symptoms, including speech arrest and perseverations, the patient recovered quickly but partially. The resection cavities from the first and second surgery were used as seeds to investigate structurally and functionally disconnected circuits in a Lesion Network Mapping (LNM) analysis. As a control, SMA-complex region was included in LNM analysis.

Results

Structural disconnection analysis revealed common disconnections between second surgery resection cavity and SMA region, at the level of the Cingulate and Superior Longitudinal Fasciculus. Also, functional analysis showed greater second surgery induced disconnection in critical hubs of the Fronto-Parietal and Default Mode Networks, as well as functional disconnection involving the spared SMA complex.

Discussion

Here the SMA syndrome, emerged despite no SMA lesion, appears to results from an alteration of structural and functional brain circuits, according to the hodotopical theory. We can speculate that disruption of interconnected networks may underlie symptom manifestation in SMA syndrome and may offer a potential framework for studying disconnection-related mechanisms.