NEW ORLEANS—A triggering peripheral cause can be identified at least three years before the onset of sporadic Parkinson’s disease in about 91% of cases, according to research presented at the 2013 Annual Meeting of the American Neurological Association. Triggering factors include a habitual sleep posture, trauma and persistent pain, and/or peculiar and persistent motor habits.
If such factors are detected early, “remission is possible before irreversible destruction of the substantia nigra,” reported Gobinathan Devathasan, MD, a neurologist at the Mount Elizabeth Medical Centre in Singapore.
The findings are based on 140 patients with early Parkinson’s disease who were responsive to levodopa. Patients were questioned regarding their sleeping posture and position. Habitual sleepers were defined as having greater than 70% of their sleep time in either the right, left, supine, or prone position; others were grouped as nonhabitual or turning sleepers. The investigators also inquired about trauma and persistent pain, as well as peculiar and persistent motor habits and intense sport activities.
The study authors identified a preceding triggering peripheral cause at least three years before disease onset in 128 patients. Among the 50 patients with muscle ultrasound performed in all four limbs, 45 “showed 4- to 7-Hz discharge even in the clinically unaffected side,” noted Dr. Devathasan. About 56% of patients were habitual or nonturning sleepers (75% when overlapping factors were considered), and in 80% of this group, onset was on the habitual side slept for arm/leg or supine position for trunk/jaw. Seventeen percent of patients had peculiar and persistent motor habits, 16% had trauma and persistent pain, and 6% engaged in extreme sports. Nineteen cases of remission occurred when the triggering cause was eliminated.
“Neurologists have been tardive to accept a peripheral initial cause because the most common factor—habitual nonturning—has not been identified as yet,” stated Dr. Devathasan. “Moreover, the gating theory sounds weak, and there was no alternative convincing mechanism.
“Increased muscle spindle activity in one limb or trunk eventually resets the whole body’s proprioceptive muscle afferents in a nonlocality or entanglement fashion,” Dr. Devathasan theorized. “Indirect evidence is abnormal muscle ultrasound in apparently unaffected limbs. Massive continual assault of afferent proprioceptive impulses on the basal ganglia and indirectly inhibitory dopaminergic fibers of the substantia nigra eventually depletes and destroys these cells. Stress-mutative changes may result.”
—Colby Stong