Some patients affected by advanced Parkinson’s disease may suffer from cognitive disorders and more generally from a specific form of dementia.

There are other neurodegenerative diseases that can cause both motor and cognitive impairment: dementia with Lewy bodies, progressive supranuclear palsy, multiple system atrophy and corticobasal degeneration.

Lewy body dementia

It is characterized by the existence of lesions called Lewy bodies.

Progressive supranuclear palsy

This disease, also called Steele-Richardson-Olszewski disease, usually begins after the age of 40. Its prevalence is 1.4/100,000 versus 100 to 170/100,000. It is characterized by a decline in ocular motor skills (especially vertical gaze), postural instability with frequent falls and akinesia.

There are differences with Parkinson’s disease:
– Significant axial stiffness in the neck.
– Dysarthria (speech disorder linked to neurological impairment).
– Dysphagia (discomfort in swallowing).
– Minor tremor.
– Significant postural problems.
– Motor disorders do not improve after treatment with L-dopa or a dopaminergic agonist.
– Cognitive disorders of the frontal type appear during the evolution.

These disorders are caused by damage to the basal ganglia and brainstem, with the presence of neurofibrillary tangles including the abnormal form of tau protein.

Multiple system (or multiple system) atrophy

It is a set of neurodegenerative diseases including:
– degeneration of the nigrostriatal pathway, with an extrapyramidal syndrome characterized by rigidity and akinesia. The damaged cerebral structures are the substantia nigra and striatum and involved in motricity are affected.
– Shy-Drager syndrome, with dysautonomia (dysfunction of the autonomic nervous system. 
– Olivo-pontocerebellar atrophy with cerebellar syndrome. The cerebral structures called pons nuclei and the cerebellum are affected. 

The occurrence of cognitive disorders can be observed in advanced forms. Levodopa (reference treatment for Parkinson’s disease) only partially responds to the extrapyramidal syndrome.

Corticobasal degeneration

It is caused by damage to the frontal and temporal cortex, as well as damage to the basal ganglia. The neurons are said to be ballooned  (ie swollen) and surrounded by glial cells which proliferate (we speak of a phenomenon of gliosis).

Clinically, the disease is characterized by apraxia and extrapyramidal syndrome.

Apraxia often begins in one part of the body, causing the inability to perform elaborate movement, despite good understanding and normal muscle strength.

The extrapyramidal syndrome is asymmetrical, even unilateral and is limited to akinesia and rigidity. However, there may be postural tremor, dystonic disorders usually beginning in the upper limb, myoclonus (rapid, involuntary, low-amplitude muscle contraction) and apraxic disorders.

The cognitive impairment appears during the evolution with behavioral disorders and signs of frontal dementia. Treatment with levodopa (or L-Dopa) has no effect. Myoclonus can be treated with clonazepam (a benzodiazepine).