Essential tremor (ET) is considered the most common movement disorder, affecting millions of people. Roughly half of ET cases appear to run in the family – that is, other members of the family tree have also had ET. But what if a person has ET yet there is no known family history? It may seem like a random occurrence. However, there is a personal medical history question that should probably be asked: Did you ever have a head injury?
Head trauma and ET
Any injury to the head, whether external (a bump or blow to the head) or internal (brain bleeding or blood vessel blockage, vascular malformation, infection, etc.) can increase the risk of developing ET. While there are head injuries severe enough for a person to lose consciousness, as in most cases of concussion, even a mild-to-moderate incident is correctly termed a head trauma. In other words, it may not take much of a blow to disrupt the brain’s normal communication pathways. Studies such as that by Benito-León, et al have shown that there is an increased risk of developing ET after brain injury, especially after age 40.
In a 2004 study, “Posttraumatic Movement Disorders after Moderate or Mild Head Injury,” Krauss et al. completed an average of 5 years of follow-up with 16 patients who developed tremors after a head injury. The observable tremors appeared similar to ET. For the majority of the patients (12 out of 16) their tremors resolved over time, but for the other four their symptoms persisted.
Fifteen years earlier, Biary et al. wrote “Post-Traumatic Tremor” about seven individuals who had mild head trauma and within 1-4 weeks developed tremor symptoms similar to ET. The authors noted that imaging revealed normal findings with nothing remarkable and labeled this as a rare complication of head trauma. However, the patients faced the same conditions as others with ET who turn to medication for symptom relief. “Clonazepam administration resulted in tremor reduction in three patients and propranolol decreased tremor in one patient.”
In fact, there is a type of tremor called Holmes tremor that specifically occurs after head injury. It is also considered rare and can be misdiagnosed as ET or other condition because it involves a “combination of resting, postural, and action tremors. It is usually caused by lesions involving the brainstem, thalamus, and cerebellum. It is often difficult to treat, many medications have been used with varying degrees of success.” With Holmes tremor, there can be a variety of other symptoms in addition to tremor: dystonia, ataxia, speech difficulties, etc.
In a 2016 paper, Raina et al. analyzed the clinical histories of 29 Holmes tremor patients. Age at the time of injury ranged from 8-76 years, and the average period from the injury to the onset of tremor was 2 months. The most common brain injury (48.3%) was stroke (bleed or blockage), followed by head trauma (17.24%) and a variety of other causes (34.5%). MRI revealed that 87.2% of the patients had lesions in the cerebellum (responsible for motor function), or thalamus (relays signals along the movement pathway), or midbrain (eye movements, auditory and visual processing). The authors noted, “Levodopa treatment was effective in 13 out of 24 treated patients (54.16%) and in 3 patients unilateral thalamotomy provided excellent results.” Interestingly, Levodopa is the medication used to control tremors due to Parkinson’s disease, and unilateral (one side) thalamotomy is what Sperling Neurosurgery Associates offers to control ET.
Biomarkers and head trauma: a possible “alert” for tremor risk
According to a new 2018 paper by Bazarian et al, “More than 50 million people worldwide sustain a traumatic brain injury (TBI) annually.” While many will fully recover with no apparent symptoms, many more will suffer temporary or permanent motor, cognitive or psychological impairment to one degree or another. Prompt intervention (diagnosis and treatment) is crucial to reduce the aftereffects, but CT scans of the brain are “overused and resource-intensive.” Bazarian’s research team developed and tested a simple blood test that can detect brain injury by measuring two proteins called UCH-L1 and GFAP. When the levels are elevated beyond a certain point, they have high accuracy in indicating that a brain injury has occurred. This, then, warrants a CT scan to identify the injured area. However, if levels are below the cut-off point, it is possible to avoid the scan. Knowing that a brain trauma has occurred may serve as an alert for possible onset of tremors or other symptoms that may show up later and help avoid worry and panic should they occur. Often, they will resolve on their own if they are mild.
Unilateral thalamotomy using MRgFUS
Our Center provides the above-mentioned treatment, unilateral thalamotomy, to control ET that is not responding to medication (or the individual does not wish to use medication). Our approach, MRI-guided Focused Ultrasound, is a noninvasive out-patient treatment using ultrasound energy to block the brain’s tremor signals to the hand. It is immediately effective and gives lasting results. Whether ET is inherited, the permanent result of an early head injury, or a random occurrence, it can progress to severe impairment of hand use. For more information, visit Sperling Neurosurgery Associates.
iAlqwaifly, M. Treatment responsive Holmes tremor: case report and literature review. Int J Health Sci (Qassim). 2016 Oct; 10(4):558-62.