A study published in the January issue of the Annals of Neurology found that neurofibrillary tangles in the substantia nigra, a part of the brain that is subject to cell loss in Parkinson's disease, are associated with gait impairment in older persons with and without dementia.
Neurofibrillary tangles are a classic brain abnormality seen in Alzheimer's disease. The more tangle pathology in the substantia nigra, the more impaired the person's gait was before death.
"Older persons without Parkinson's disease often exhibit parkinsonian signs, such as difficulty with walking and balance (gait impairment), slowness in movements, rigidity and tremor," said study author Dr. Julie Schneider of the Rush Alzheimer's Disease Center. "The mild parkinsonian signs associated with aging have been historically viewed simply as an expected sign of aging rather than a disease process. Previous studies have shown that at least one of these signs, gait impairment, has harmful effects in older persons, and our current study suggests why this may be the case."
The study included 86 autopsied subjects from the Religious Orders Study, a longitudinal clinical-pathological study of aging and dementia. Participants of the Religious Orders Study are older Catholic clergy who enroll without known dementia and agree to annual follow-up and brain donation at death.
The study included persons with and without dementia but excluded people with idiopathic Parkinson's disease. Though less than half of the subjects had dementia, the study found nearly 78 percent of test subjects had neurofibrillary tangles in the substantia nigra. Annual neurological examinations included an assessment of parkinsonian signs using the Unified Parkinson's Disease Rating Scale. All 86 persons had at least some evidence of parkinsonian signs before death. Gait was the most severely affected domain followed by bradykinesia (slowness in movement), rigidity, and tremor.