From the Guidelines
Intention tremor in Multiple Sclerosis (MS) is primarily associated with lesions in the infratentorial region, specifically in the cerebellum and its connections, including the cerebellar peduncles. This association is based on the assessment of lesions on magnetic resonance imaging in MS patients, as described in a 2019 study published in the journal Brain 1. The study highlights that infratentorial lesions, which are defined as T2-hyperintense lesions in the brainstem, cerebellar peduncles, or cerebellum, are commonly found near the surface or in a central location with an ovoid/round shape.
Key Findings
- Infratentorial lesions are frequently located in the pons, contiguous with the cisterns or involving the floor of the fourth ventricle, and may affect the medial longitudinal fasciculus or the pontine trigeminal root entry zone 1.
- Lesions in the midbrain are often found in the cerebral peduncles and close to the periaqueductal grey matter, while in the medulla oblongata, they typically have a uni- or bilateral paramedian location 1.
- The cerebellar pathways, including the superior cerebellar peduncle, are critical in the development of intention tremor, as they disrupt the coordination of voluntary movements by affecting the cerebellum's ability to regulate the timing and force of movements.
Clinical Implications
- Intention tremor in MS patients is characterized by a tremor that worsens as the patient approaches the target during goal-directed movements, and is often accompanied by other cerebellar symptoms such as dysmetria, dysdiadochokinesia, and ataxic gait.
- The tremor is typically more pronounced in the upper limbs and can significantly impact daily activities requiring fine motor control.
- The involvement of the dentatorubrothalamic tract, which connects the cerebellum to the thalamus and motor cortex, can also contribute to intention tremor in MS patients.
From the Research
Location of Lesion Associated with Intention Tremor in Multiple Sclerosis (MS)
- The lesion associated with intention tremor in Multiple Sclerosis (MS) is located in the brainstem, specifically in the pons 2.
- Studies have shown that intention tremor amplitude is significantly related to lesion load in the brainstem, but not in the cerebellum 2.
- The correlation between tremor amplitude and lesion load is particularly strong in the contralateral pons, and patients with more severe tremor in both arms have a greater lesion load bilaterally in the pons 2.
- Other studies have discussed the treatment of intention tremor in MS, including the use of electromagnetic fields 3, botulinum toxin type A 4, and deep brain stimulation 5, 6, but these do not provide direct evidence on the location of the lesion.
- Overall, the evidence suggests that the lesion associated with intention tremor in MS is located in the brainstem, particularly in the pons 2.