Multiple Sclerosis: The Temperature-Cognitive Status Connection

By Sanjai Sinha, MD
Reviewed By Claire S. Riley, MD, Assistant Professor of Neurology and Director, Columbia University Multiple Sclerosis Clinical Care and Research Center, New York, NY

Multiple sclerosis (MS) is the most common autoimmune inflammatory demyelinating disease of the central nervous system, affecting an estimated 250,000 to 350,000 Americans, according to the National Institute of Neurological Disorders and Stroke. Typical clinical manifestations of MS include optic neuritis; sensory symptoms, such as numbness and tingling; Lhermitte’s phenomenon (electric shock sensation down the spine and radiating to the limbs in response to neck flexion); motor symptoms, such as muscle weakness or paralysis, and spasticity; and autonomic abnormalities, including bowel, bladder, and sexual dysfunction. These symptoms are often exacerbated by warmer outdoor temperatures, known as Uhthoff’s phenomenon.¹ A survey of over 2500 patients confirmed heat as a major cause of MS symptom exacerbation, and research into the relationship between temperature and cognitive changes in MS patients has begun in earnest.²

Cognitive impairment, as assessed by neuropsychological testing, may be common even among patients with a recent MS diagnosis. Frequent abnormalities include problems with abstract conceptualization, long-term and recent memory, complex attention, and efficiency and speed of information processing.³ Given that up 40% to 65% of patients with MS have cognitive abnormalities at some point in their disease,^3,4it’s an area that many MS researchers and clinicians would like to understand better. Two recent studies examined this relationship and investigated the neurophysiologic basis using functional magnetic resonance imaging (fMRI).

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