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The term "startle" describes a sudden involuntary movement of the body in response to an unexpected stimulus. The startle reflex in humans is a normal physiologic symmetric flexor response present starting around 6 weeks of age and remaining for life. Conditions with an abnormal or exaggerated startle are collectively referred to as startle syndromes, and are a rare, heterogeneous group of disorders. The startle syndromes are categorized into three broad groups: (1) hyperekplexia, (2) stimulus-induced disorders, and (3) neuropsychiatric startle disorders. While startle syndromes are often relatively benign, medical emergencies can arise as complications from the abnormal startle. Most concerning is the increased morbidity and mortality from apneic episodes in patients with hyperekplexia, which can unfortunately lead to sudden death. Therefore, prompt recognition and treatment of this disorder is imperative. In this chapter, we review the normal human startle reflex and then provide an overview of the startle syndromes, with a particular focus on hyperekplexia given the movement disorder emergencies seen in this syndrome.
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Background/UNASSIGNED:gene have recently been linked to a spectrum of phenotypes including epilepsy, cerebellar ataxia, cortical myoclonus and intellectual disability (ID), and primary congenital defects of glycosylation. Case Report/UNASSIGNED:-associated clinical phenotypes. Discussion/UNASSIGNED:should be included in the genetic screening of undiagnosed forms of myoclonus, myoclonus-ataxia, and progressive myoclonus epilepsies.

Huntington disease, a neurodegenerative disease characterized by progressive motor, behavioral, and cognitive decline, is caused by a CAG trinucleotide repeat expansion in the huntingtin gene on chromosome 4. Current treatments target symptom management because there are no disease-modifying therapies at this time. Investigation of RNA-based and DNA-based treatment strategies are emerging and hold promise of possible future disease-modifying therapy.

INTRODUCTION/BACKGROUND:Myoclonus is a hyperkinetic movement disorder characterized by sudden, brief, lightning-like involuntary jerks. There are many possible causes of myoclonus and both the etiology and characteristics of the myoclonus are important in securing the diagnosis and treatment. Myoclonus may be challenging to treat, as it frequently requires multiple medications for acceptable results. Few randomized controlled trials investigating the optimal treatment for myoclonus are available, and expert experience and case series guide treatment. Areas Covered: In this article, the authors review the basics of myoclonus and its classification. The authors discuss the current management of myoclonus and then focus on recent updates in the literature, including both pharmacologic and surgical options. Expert opinion: Myoclonus remains a challenge to manage, and there is a paucity of rigorous clinical trials guiding treatment paradigms. Furthermore, due to the etiological heterogeneity of myoclonus, defining the appropriate scope for high quality clinical trials is challenging. In order to advance the field, the myoclonus study group needs to be revived in the US and abroad so that interested investigators can collaborate on multicenter clinical trials for myoclonus treatments.

In this review, we summarize recent advances in understanding the etiology, risk factors and pathophysiology of focal task specific dystonia (FTSD), movement disorders characterized by abnormal motor activation during the performance of specific, repetitive actions. We focus on two common FTSD, musician's dystonia and writer's cramp. FTSD may pose a threat to the patient's livelihood, and improved therapeutic treatments are needed.

INTRODUCTION/BACKGROUND:Although it is not rare for magnetic resonance imaging findings in Creutzfeldt-Jakob disease to be asymmetric, unilateral clinical syndromes are uncommonly reported and may confound diagnosis. In addition, neurological paraneoplastic syndromes are not common in renal cell carcinoma, though there are cases reported, often without an offending antibody isolated. CASE REPORT/METHODS:A 66-year-old man was admitted with 1 month of left-sided numbness and "loss of control" of the left arm. Examination revealed action-induced irregular jerking movements of the left arm. Mental status testing was normal. Magnetic resonance imaging brain revealed patchy areas of restricted diffusion along the cerebral cortices. Screening computed tomographic scans revealed innumerable lung nodules compatible with metastases, as well as a renal mass consistent with renal cell carcinoma. Lumbar puncture was performed and cerebrospinal fluid was sent for paraneoplastic autoantibody evaluation and protein 14-3-3. Over the next week the patient developed dystonic posturing of the left arm, left leg jerking movements, a right arm action tremor, and cognitive impairment. Paraneoplastic autoantibodies were negative. Protein 14-3-3 was elevated and brain biopsy revealed spongiform encephalopathy with positive immunoblotting. The patient died about 2 months from symptom onset. CONCLUSIONS:Creutzfeldt-Jakob disease can present with entirely unilateral myoclonus and numbness, without specific complaints of cognitive impairment. Not every difficult or unclear neurological syndrome in a patient with metastatic cancer is a paraneoplastic syndrome.