• History and Examination
     
    53 year old LH man presents with 5 year history of bilateral (L>R) hand tremor. He first noticed the tremor in the left 5th finger. Over time the entire hand was involved, and he also developed stiffness of the arm. He has been treated with levodopa/carbidopa (Sinemet), which initially helped.

    As the years passed, his symptoms worsened, with increasing tremor in both hands and slowing of his gait.

    On exam, he has a resting tremor in both hands, more noticeable on the left. Holding his arms outstretched or in a winged position especially accentuates the tremor. His spiral drawing (left hand) is shown in the figure. There is mild L>R rigidity in both arms, and rapid alternating movements of both hands are slightly slow and clumsy. His gait is moderately wide based and slow, with short stride length and poor heel strike. Left arm swing is reduced.

    DBS surgery is performed using microelectrode recordings to map the target. His spiral drawing after the MER is shown on top. After placement of the DBS lead into the chosen target location, before even turning it on to test stimulation effects, his spiral drawing is tested again (bottom).

    Figure 1

     

    Figure 2

    1. What is the most likely diagnosis?

    2. Which of the following would be a reason against offering DBS?

     

    3. His most bothersome symptom is the hand tremor, which occurs both at rest and when he tries to perform simple tasks such as eating, dressing, and writing. Which brain region would be the best target to treat his resting and action tremor, and also help.

    4. What is the term given to the improvement in his spiral drawing following MER, and further improvement following placement of the lead?

    5. Which of the following describes you?

    6. I practice in one of the following locations.

    7. Comments
     
    • I had the opportunity to practice small lesions in the ventro-lateral thalamic nucleous in patients with parkinson tremor and rigidity in 1.964-68 with stereotactic lesion under radiologic images control, and this gave good control of tremor and rigidity for three or 4 years,then stop the method with the levodopa treatment.
    • Nice case
    • GPi is also a valid target, neuropsych testing was not mentioned but should be done prior to DBS in PD cases.

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    Case Explanation:

    The patient’s history and exam are consistent with Parkinson disease (PD), which is characterized by tremor, rigidity, and bradykinesia. Essential tremor (ET) is characterized by a predominantly action (not resting) tremor, and dystonia by stiffness and unwanted muscle contractions causing twisting movements or uncomfortable postures.

    Levodopa/carbidopa (Sinemet) is a common medication used to treat PD. Important red flags in the consideration for DBS include signs/symptoms of other disorders such as multi-system atrophy (MSA). MSA may present with dysautonomia, ataxia, and possibly progressive dementia (suggestive of Lewy body disease). Because MSA does not improve with DBS, this entity should be ruled out when evaluating potential DBS candidates. Initial response to Sinemet with waning benefit over time is typical of idiopathic PD and a predictor of good response to DBS. Twisting movements that develop following prolonged Sinemet treatment are dyskinesias and are common in PD. Motor fluctuations are also common in PD and respond well to DBS. Freezing of gait may not respond well to DBS, so lack of freezing is a positive sign.

    Common targets for DBS for PD include the STN, GPi, and Vim. Vim DBS is effective for treating action tremor, whether a symptom of PD or ET, but typically does not improve bradykinesia or rigidity. STN and GPi DBS are known to improve resting tremor, rigidity, and bradykinesia, but may have limited benefit for action tremor. The caudal portion of the zona incerta (cZI) has been suggested as a target for tremor-predominant PD, as DBS of the cZI can help both resting and action tremor, as well as the other cardinal symptoms of PD.

    The improvement in the patient’s symptoms following MER and lead placement is called a microlesion effect. The act of penetrating the target region with a microelectrode or even larger DBS lead causes enough local disruption to produce the clinical effect of a small lesion. This effect is typically temporary.

    References:

    • DeLong, M. R., & Wichmann, T. (2015). Basal Ganglia Circuits as Targets for Neuromodulation in Parkinson Disease. JAMA Neurology, 72(11), 1354–1360. doi:10.1001/jamaneurol.2015.2397
    • Blomstedt, P., Fytagoridis, A., Åström, M., Linder, J., Forsgren, L., & Hariz, M. I. (2012). Unilateral caudal zona incerta deep brain stimulation for Parkinsonian tremor. Parkinsonism & Related Disorders, 18(10), 1062–1066. doi:10.1016/j.parkreldis.2012.05.024
    • Tykocki, T., Nauman, P., Koziara, H., & Mandat, T. (2013). Microlesion effect as a predictor of the effectiveness of subthalamic deep brain stimulation for Parkinson's disease. Stereotactic and Functional Neurosurgery, 91(1), 12–17. doi:10.1159/000342161
    • Herrington, T. M., Cheng, J. J., & Eskandar, E. N. (2016). Mechanisms of deep brain stimulation. Journal of Neurophysiology, 115(1), 19–38. doi:10.1152/jn.00281.2015

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