A 67-year-old woman could eat soup, cut food with a knife and fork, and drink from a glass without trouble. But every time she raised her right hand to apply lipstick, her arm and shoulder broke into brief, repetitive jerks.
The movements had begun about six months after a fall that directly injured her right shoulder, and she had lived with them for five years by the time she was referred to neurologists. Francesco Cavallieri, Elena Moro, Valérie Fraix and colleagues described the case in 2019 in Tremor and Other Hyperkinetic Movements, naming it a task-specific “lipstick dystonic tremor.”
The most surprising finding came when doctors asked her to pretend.
Miming the Motion Changed Nothing
The right-handed woman had no family history of neurological disease. Her fall had caused shoulder pain, bruising, swelling, and stiffness. An X-ray found no bone damage, and she was sent home in a sling-style immobilizer. The injury symptoms cleared in about three weeks, followed by a brief course of physical therapy.
Months later, the jerking appeared in her right arm and shoulder.
Doctors then had her mimic putting on lipstick while holding her arm in exactly the same position. No jerks appeared. Only the real act triggered them. That, the authors wrote, showed the disorder was task-specific rather than position-specific, meaning the action itself, not the arm’s posture, was the trigger.
Distraction with other motor tasks did not change the movements, and there was no sign of suggestibility, features that help distinguish this kind of disorder from a functional movement disorder.
The distinction between task and position is more than a technicality. A tremor triggered by posture should appear whenever the arm is held a certain way, whatever the person is doing. Hers appeared only when she actually performed one familiar, well-practiced action, which is the defining feature of task-specific movement disorders such as writer’s cramp.
Muscle Recordings and Normal Scans
Recordings of muscle activity showed pseudorhythmic bursts, averaging about five per second and lasting about 78 milliseconds, that appeared during the lipstick action. The bursts showed up in several shoulder and chest muscles: the pectoralis major and minor, the deltoid and the teres major.
An MRI of her brain showed only age-related white matter changes. An MRI of her cervical spine was normal.
When Injury Comes Before Abnormal Movement
The authors classified the case as a peripherally induced movement disorder, a condition in which abnormal movements follow trauma to a body part outside the brain and spinal cord. The National Institute of Neurological Disorders and Stroke lists trauma among the causes of acquired dystonia, and the Cleveland Clinic notes that focal dystonia symptoms sometimes start after an injury.
Doctors use criteria proposed in 1995 by neurologists Francisco Cardoso and Joseph Jankovic to judge whether an injury plausibly caused a movement disorder. They weigh how severe the trauma was, whether the movements arose in the same body region, and how much time passed in between. The authors wrote that their patient met those criteria, and that a coincidental cause was unlikely given the absence of any other obvious explanation.
The label itself may also be shifting. A 2025 editorial in the journal Dystonia noted that it remains unclear whether task-specific tremor should be classified as a form of task-specific dystonia. The editors also wrote that repetitive jerky movements of a body part in dystonia should no longer be classified as tremor, a change that could affect how cases like this one are described in the future.
Injections Brought Relief
Her doctors injected botulinum toxin into the clavicular head of the pectoralis major, guided by muscle recordings. Within three weeks, the movements had decreased.
Botulinum toxin injections are often the most effective treatment for focal dystonia, according to the National Institute of Neurological Disorders and Stroke. Relief usually begins within a few days and lasts several months, which is why the shots are repeated.
She went on to receive repeat injections about every five months, roughly 100 units divided among the pectoralis major, deltoid, and teres major. The improvement in function persisted, and a video recorded about two months after a later injection showed near-complete resolution.
That result stands out. The authors cited a literature estimate that botulinum toxin relieves symptoms in only about 20% of peripherally induced movement disorders.
The case report involves a single patient, so it cannot show how often shoulder injuries lead to task-specific movement problems. Most people who injure a shoulder recover without any such complication.
Anyone who develops new involuntary movements after an injury, particularly movements tied to one specific action, should tell their doctor and consider evaluation by a movement disorders specialist. Sudden weakness, numbness, or loss of coordination on one side of the body requires emergency care.
Key Questions Answered
What happened to the woman?
About six months after a fall injured her right shoulder, her right arm began jerking whenever she applied lipstick, but not during other everyday tasks.
Why did doctors call it task-specific?
Miming the lipstick motion in the identical arm position did not trigger the jerks. Only the real action did.
What is a peripherally induced movement disorder?
An abnormal movement that develops after injury to a body part outside the brain and spinal cord. It is rare, and how it arises is debated.
What did tests show?
Muscle recordings showed rhythmic bursts in shoulder and chest muscles. Brain and neck MRIs showed no cause.
How was she treated?
With botulinum toxin injections about every five months, which produced lasting improvement and near-complete resolution on video after one injection.
Do shoulder injuries usually cause this?
No. The condition is rare, and most people recover from shoulder injuries without it.
Published by Medicaldaily.com
