Emotional lability

Around a third of all MND patients experience labile affect, also known as emotional lability, pseudobulbar affect, or pathological laughter and crying. Patients with pseudobulbar palsy are particularly likely to be affected, as are patients with PLS.

Effects on cognition, mood, and senses

Cognitive change occurs in between 33–50% of patients. A small proportion exhibit a form offrontotemporal dementia characterised by behavioural abnormalities such as disinhibition, apathy, and personality changes. A small proportion of patients may also suffer from an aphasia, which causes difficulty in naming specific objects. A larger proportion (up to 50%) suffer from a milder version of cognitive change which primarily affects what is known as executive function. Briefly, this is the ability of an individual to initiate, inhibit, sustain, and switch attention and is involved in the organisation of complex tasks down to smaller components. Often patients with such changes find themselves unable to do the family finances or drive a car. Depressionis surprisingly rare in MND (around 5–20%) relative to the frequency with which it is found in other, less severe, neurological disorders e.g. ~50% in multiple sclerosis and Parkinson's disease, ~20% in Epilepsy. Depression does not necessarily increase as the symptoms progress, and in fact many patients report being happy with their quality of life despite profound disability. This may reflect the use of coping strategies such as reevaluating what is important in life.

Although traditionally thought only to affect the motor system, sensory abnormalities are not necessarily absent, with some patients finding altered sensation to touch and heat, found in around 10% of patients. Patients with a predominantly upper motor neurone syndrome, and particularly PLS, often report an enhanced startle reflex to loud noises.

Neuroimaging and neuropathology has demonstrated extra-motor changes in the frontal lobes including the inferior frontal gyrus, superior frontal gyrus, anterior cingulate cortex, and superior temporal gyrus. The degree of pathology in these areas has been directly related to the degree of cognitive change experienced by the patient, if any. Patients with MND and dementia have been shown to exhibit marked frontotemporal lobe atrophy as revealed by MRI or SPECT neuroimaging.