Neurological reserve in multiple sclerosis
#Atrophy #Cognition #Early Damage
  • Neurological Reserve is a finite natural process that helps compensate for MS symptoms by rewiring the brain1
  • Neurological Reserve comprises of 2 components: Brain Reserve and Cognitive Reserve1
  • Lifestyle choices can influence Neurological Reserve2

A Finite Function

In multiple sclerosis (MS), the patient’s immune system attacks nerve fibers in the brain and spinal cord causing inflammation, demyelination, nerve damage, and the destruction of axons and neurons.1,3 Throughout time, this neurological damage can lead to debilitating physical and cognitive impairment.1 In patients with relapsing forms of MS, this damage can often be redressed—causing symptoms to temporarily fade—due to a natural compensatory process known as Neurological Reserve.1

Neurological Reserve in Patients With MS

Neurological Reserve compensates for the pathological damage of MS by rerouting signals or adapting undamaged areas of the brain to take on new functions.1 Though Neurological Reserve can help preserve both cognitive function and physical ability, it has a finite capacity and will eventually fail as MS progresses.1 Evidence shows that cognitive impairment occurs early in the disease course, and the process of Neurological Reserve can mask this damage leading to MS being undiagnosed and untreated for years.1

Image of neurological reserve process
Image of the Neurological Reserve process where brain signals are shown rerouting around MS lesion damage.1

The Mechanism of Neurological Reserve

Neurological Reserve comprises 2 components that help independently protect against cognitive decline caused by MS—Brain Reserve and Cognitive Reserve.1

Brain Reserve is determined by brain volume, linking the size of the brain to the degree of cognitive impairment experienced by the patient. It is hypothesized that a larger brain will be more resistant to physical impairment, particularly in elderly and MS patients. Brains with greater volume tend to have a higher neuronal count, which in turn builds strong neuronal networks that protect against disruption.4 In a 2016 clinical study (N=52), Sumowski and colleagues found that patients who progressed in their physical disability had lower baseline brain volume and worse brain volume loss over time.4 Cognitive Reserve is another mechanism for coping with pathology that focuses on the brain’s ability to sustain disruption and continue operating efficiently.1,5 With Cognitive Reserve, an individual with a higher intelligence level or educational/occupation attainment can withstand greater brain damage before their cognitive performance begins to suffer.5 Consequently, studies suggest that disease severity in patients with a higher education and a more advanced pathology is comparable to patients with lower education and less pathology.5

Exhausting the Neurological Reserve

Although Neurological Reserve can help minimize some of the effects of disease progression, it is ultimately a finite resource. When a patient’s Neurological Reserve is depleted, MS symptoms are more likely to progress, including both cognitive and physical symptoms.1,6,7 The impact of cognitive impairment can be extremely debilitating to patients’ daily lives affecting their attention span, performance, and ability to not only commit new information to memory, but also recall information that was previously learned. In one study, 66% of patients with MS (N=426) experienced deficits in at least 1 recall task.8 Physical symptoms commonly associated with MS include sensory disturbances (40% of patients with MS), motor dysfunction (39%), visual impairment (30%), and fatigue (30%).1 Diagnosing MS early is integral in order to help maintain Neurological Reserve for as long as possible and prevent MS symptoms from progressing further.1

Lifestyle and Neurological Reserve

As previously stated, Neurological Reserve is a finite function—however, both components can be maintained and built upon by the lifestyle choices patients make each day.1,2 Common lifestyle choices encouraged in managing MS are aerobic exercises, a healthy diet, and a sufficient sleep schedule, all shown to improve both brain volume (Brain Reserve) and processing speed (Cognitive Reserve).1,6 When studying tobacco smoking and disability progression in MS (N=895), Manouchehrinia et al found that smokers with MS not only accumulated more disability during a shorter period of time, but also experienced a more severe disease than nonsmokers.9 Cognitive Reserve can be enhanced separately through enriching life experiences like reading books, playing a musical instrument, and creating art.10 These cognitive leisure activities independently aid both cognitive efficiency and memory even more so than Brain Reserve.10

A Notable Takeaway

Neurological Reserve is a powerful, compensatory mechanism that can help minimize the impact of axonal loss and neurodegeneration.1 Because early damage can impact Neurological Reserve, it is important to help preserve this finite resource with practical lifestyle choices and informed treatment decisions to help patients maintain a healthy and well-functioning brain.1,7

 

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