On the relation between self-reported cognitive fatigue and the posterior hypothalamic-brainstem network.

Area of Science:

• Neuroimaging
• Neurology
• Neuroscience

Background:

• Fatigue is a common symptom in multiple sclerosis (MS).
• The exact causes of MS-related fatigue are not fully understood.
• Hypothalamus-brainstem pathways are implicated in sleep-wake cycles and hypothalamic function during inflammation.

Purpose of the Study:

• To investigate the integrity of hypothalamus-brainstem fibres in MS patients with and without cognitive fatigue.
• To explore the role of these fibres in regulating hypothalamic activation and wakefulness.

Main Methods:

• Diffusion-tensor imaging (DTI) based tractography was used to analyze hypothalamus-brainstem fibre integrity.
• Participants included MS patients with/without self-reported cognitive fatigue and healthy controls.
• Analysis focused on anterior, medial, and posterior hypothalamic areas, controlling for clinical factors and depression.

Main Results:

• MS patients without fatigue exhibited increased axial and radial diffusivity in fibres connecting the right posterior hypothalamus to the right locus coeruleus.
• No significant differences were found in medial hypothalamus or corpus callosum fibres.
• Brain atrophy and lesion load did not explain these findings.

Conclusions:

• Altered diffusivity in posterior hypothalamus-brainstem fibres in non-fatigued MS patients may suggest a mechanism for regulating wakefulness.
• This alteration might prevent excessive hypothalamic activation, potentially downregulating structures involved in wakefulness and exploration.