Neuronal ceroid lipofuscinosis (NCL for short) is the umbrella term given to a hereditary health condition that can affect a reasonably wide number of different dog breeds, and leads to a range of out of character behaviours and symptoms in affected dogs including hallucinations, fits, bouts of hyperactivity and potentially, out of character outbursts of aggression. As the condition progresses, affected dogs lose their coordination and muscle control, leading to stumbling, clumsiness, epileptic fit and problems exercising normally.

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Most animals lose their ability to coordinate everyday muscular activities. As the extent of neurodegeneration increases, all affected dogs develop psychological abnormalities and ataxia.