WBR0574

Author	[[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathophysiology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 66-year-old woman, who had a recent hip fracture after a fall, presents to the neurology clinic with complaints of hand tremor for the past few months. Although the tremor has not significantly worsened over time, the patient explains that it is very bothersome and interferes with her daily activities. The patient notices the tremor only when she performs activities that require use of her arms. On physical examination, the physician notes an absence of a baseline tremor; but when the patient is asked to reach for a pen, she exhibits a slow, coarse, zigzag motion of her hand as she extends for it. The tremor increases in intensity as the patient’s hand gets closer to the object. Also, the patient often overshoots and often requires a few attempts before grabbing the pen. What is the most likely cause of this patient's tremor?]]
Answer A	AnswerA::Genetic predisposition
Answer A Explanation	[[AnswerAExp::Essential or postural tremor is usually due to genetic predisposition. It is typically a tremor associated with maintenance of a certain posture (eg outstretched arms, pouring water, drinking from a cup). Essential tremor can involve the hands, the head, and even the voice. Many risk factors have been linked to essential tremor, including age, Caucasian race, and family history. Essential tremor is usually exacerbated by stress, fever, caffeine, and β-adrenergic agonists. Patients classically self-medicate with alcohol that decreases the intensity of the tremor. Treatment is usually with β-blockers.]]
Answer B	AnswerB::Excessive caffeine consumption
Answer B Explanation	[[AnswerBExp::Stress, fever, caffeine, and β-adrenergic agonists usually exacerbate a pre-existing tremor among patients with essential (postural) tremor or Parkinson's disease. Excessive caffeine consumption maylead to a low amplitude tremor among a small minority of patients with no underlying disease.]]
Answer C	AnswerC::Cerebellar lesion
Answer C Explanation	[[AnswerCExp::Intention tremor secondary to a cerebellar lesion is characterized by a slow, coarse, and zigzag motion that is observed when the patient is reaching for a target (eg finger-to-nose testing). Intention tremor becomes more prominent as the patient approaches the desired object, often missing the actual location. Intention tremor may be either bilateral or unilateral depending of the location of the cerebellar lesion.]]
Answer D	AnswerD::Dopamine depletion from the substantia nigra
Answer D Explanation	[[AnswerDExp::Parkinson’s disease involves dopamine depletion from the substantia nigra, leading to resting tremor, bradykinesia, and cogwheel rigidity. Resting tremor is the presenting complaint of the majority of patients with Parkinson’s disease. Classically, the tremor is present at rest and abates if the patient is asked to hold his hands outstretched for a period of time.]]
Answer E	AnswerE::Caudate atrophy
Answer E Explanation	[[AnswerEExp::Caudate atrophy is observed among patients with Huntington’s disease. Caudate atrophy does not usually cause tremor. Huntington’s disease typically manifests as chorea and athetosis. Chorea refers to sudden, jerky involuntary movements; while athetosis describes slow, convoluted, writhing movements usually observed in the fingers.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::Intention tremor (kinetic tremor) is a tremor that only occurs during voluntary movement. The above presentation closely represents the classical findings of intention tremor associated with cerebellar dysfunction. Intention tremor is characterized by a low frequency, coarse motion that is accentuated as the patient gets closer to a desired target. Dysmetria, defined as a lack of coordination that results in an overshoot or undershoot phenomenon that causes the patient to miss the intended target, is also often associated with intention tremor. Typically, finger-to-nose testing will reveal the tremor. Although intention tremors may be isolated events, they may be associated with ataxia or other cerebellar symptoms. This patient has a history of fall and hip fracture which may be related to her tremor. Other causes of intention tremor include multiple sclerosis and Wilson’s disease. Educational Objective: Intention tremor (kinetic tremor) is a slow, low-amplitude motion observed when a patient is voluntarily reaching for a target. It is associated with cerebellar lesions or atrophy. References: Elble RJ. Tremor: clinical features, pathophysiology, and treatment. Neurol Clin. 2009;27(3):679-95, v-vi. Louis ED. Essential tremor. Lancet Neurol. 2005;4(2):100-10. First Aid 2014 page 454]]
Approved	Approved::Yes
Keyword	WBRKeyword::Cerebellum, WBRKeyword::Intentional tremor, WBRKeyword::Essential tremor, WBRKeyword::Kinetic tremor, WBRKeyword::Cerebellar lesion, WBRKeyword::Voluntary, WBRKeyword::Movement, WBRKeyword::Intention, WBRKeyword::Tremor, WBRKeyword::Intention tremor
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