From the Guidelines
Focal movement disorders are primarily caused by abnormal electrical activity in a specific area of the brain.
Causes of Focal Movement Disorders
- Structural brain lesions: Such as tumors, infections, infarctions, traumatic brain injuries, vascular malformations, and developmental abnormalities can cause focal movement disorders 1.
- Epilepsy: Focal seizures, which are a type of epilepsy, can cause localized movement disorders, including jerking of one extremity or one side of the body, abnormal facial movements, and small repetitive movements 1.
- Neurological conditions: Conditions such as Parkinson's disease, dystonia, and functional neurologic disorders can also cause focal movement disorders, particularly in individuals with 22q11.2 deletion syndrome 1.
- Metabolic abnormalities: Hypocalcemia, hypomagnesemia, and other metabolic imbalances can induce or worsen movement disorders, including focal movement disorders 1.
Diagnosis and Treatment
- Imaging studies: MRI is the first imaging investigation for patients with focal epilepsy, which can help identify structural aetiologies such as hippocampal sclerosis, tumors, or focal cortical dysplasia 1.
- Pharmacotherapy: Antiseizure medications (ASMs) are the initial treatment of choice for focal movement disorders, but approximately 30% of patients do not respond to two ASMs and are considered drug-resistant 1.
- Epilepsy surgery: Surgery is a promising option for patients with drug-resistant focal epilepsy, with approximately 65% of patients becoming seizure-free 1.
From the Research
Causes of Focal Movement Disorders
The causes of focal (localized) movement disorders can be attributed to various factors, including:
- Neurodegenerative disorders, such as Parkinson disease, Huntington disease, and Wilson disease 2
- Functional movement disorders (FMD), which can present as various phenotypes, including tremor, dystonia, myoclonus, gait disorders, and parkinsonism 3
- Focal motor seizures, which can manifest as a defined movement disorder, such as myoclonus, dystonia, chorea, stereotypies, myoclonus-dystonia, and tremor 4
- Other conditions, such as drug-induced movement disorders, essential tremor, restless legs syndrome, and Tourette syndrome 2, 5
Relationship between Movement Disorders and Seizures
There is a significant overlap between movement disorders and focal motor epilepsy, with some movement disorders, such as dystonia, being accompanied by features of epilepsy 6
- Focal motor seizures can present with a phenomenology fulfilling diagnostic criteria for movement disorders, making diagnosis challenging 4
- A careful history and clinical examination are essential in differentiating between movement disorders and seizures 5, 6
Diagnostic Challenges
Diagnosing focal movement disorders can be challenging due to the lack of confirmatory laboratory tests or radiologic studies 5