WBR0296

Author	[[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Embryology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 32-year-old man presents to the physician’s office with complaints of progressive numbness of the arms, weakness, and hiccups. His past medical history is unremarkable, and the patient denies intake of any medications. Physical examination is remarkable for bilateral loss of pain and temperature sensations over the shoulders and the upper extremities in a cape-like distribution. The patient reports normal touch sensation and proprioception. He feels bilateral vibration sensations when a 128 Hz tuning fork is placed over the interphalangeal joints of his big toes. Which of the following diseases is most commonly associated with this patient's condition?]]
Answer A	AnswerA::Ependymoma
Answer A Explanation	AnswerAExp::Ependymoma and other brain tumors are a cause of syringomyelia, but they are not the most common cause.
Answer B	AnswerB::Chiari I malformation
Answer B Explanation	AnswerBExp::Syringomyelia is most commonly associated with Chiari I malformation (CMI), a hindbrain malformation characterized by the abnormal downward herniation of the cerebellar tonsils below the foramen magnum.
Answer C	AnswerC::Thoracolumbar myelomeningocele
Answer C Explanation	[[AnswerCExp::Myelomeningocele is a neural tube defect that is characterized by the protrusion of the spinal cord and membranes through a defective vertebral column. It involves multiple tissue layers, including the spinal cord, dura, soft tissue, and skin. Chiari II malformation is a congenital deformity of the posterior fossa and the spine that is characterized by an elongated small cerebellum, a small posterior fossa, and a caudal shift of the brainstem due to the disproportionate and rapid development of the brain tissue in the dural posterior fossa. Unlike Chiari I malformation, Chiari II malformation usually manifests early in childhood or even during the neonatal period and is almost always associated with myelomeningocele and hydrocephalus.]]
Answer D	AnswerD::Chiari II malformation
Answer D Explanation	[[AnswerDExp::Chiari II malformation is a congenital deformity of the posterior fossa and the spine that is characterized by an elongated small cerebellum, a small posterior fossa, and a caudal shift of the brainstem due to the disproportionate and rapid development of the brain tissue in the dural posterior fossa. Unlike Chiari I malformation, Chiari II malformation usually manifests early in childhood or even during the neonatal period and is almost always associated with myelomeningocele and hydrocephalus.]]
Answer E	AnswerE::Dandy-Walker syndrome
Answer E Explanation	AnswerEExp::Dandy-Walker syndrome (DWS) is the agenesis of the cerebellar vermis and cystic enlargement of the fourth ventricle. DWS is classically associated with hydrocephalus and spina bifida.
Right Answer	RightAnswer::B
Explanation	[[Explanation::Syringomyelia is a chronic neurological disease characterized by the presence of a syrinx, an abnormal fluid-filled spinal cord cavity. Clinically, syringomyelia is suspected when patients report bilateral loss of pain and temperature sensations. The lesion is usually located in the lower cervical region, where symptoms are frequently reported at a dermatome level that has a "cape-like" distribution. Since the spinothalamic tract cells cross just ventral to the central canal, the syrinx mainly affects the spinothalamic tract pathway, where an interruption occurs at the level of the axons that cross through the ventral spinal commissure. In contrast, the dorsal column-medial lemniscus and corticospinal pathways are not affected in syringomyelia, and thus the the touch, vibration, proprioception, and pressure sensations (dorsal column-medial lemniscus) and voluntary movement (corticospinal pathway) remain intact. Syringomyelia is most commonly associated with Chiari I malformation (CMI), a congenital hindbrain malformation characterized by the caudal herniation of the cerebellar tonsils at least 3-5 mm below the foramen magnum. Patients with Chiari I malformation are usually asymptomatic at childhood and may present with syringomyelia during early adulthood (25-35 years of age) or with headaches and cerebellar symptoms. Other causes of syringomyelia include trauma, brain tumors, and meningitis, but idiopathic syringomyelia is not uncommon. Educational Objective: Syringomyelia is a chronic neurological disease characterized by the presence of a syrinx, an abnormal fluid-filled spinal cord cavity. Clinically, syringomyelia is suspected when patients report bilateral loss of pain and temperature sensations in the lower cervical region with a "cape-like" distribution. Syringomyelia is most commonly associated with Chiari I malformation (CMI), a hindbrain malformation characterized by the abnormal caudal herniation of the cerebellar tonsils at least 3-5 mm below the foramen magnum. References: Naidich TP, McLone DG, Fulling KH. The Chiari II malformation: part IV. The hindbrain deformity. Neuroradiology. 1983;25:179-97. Milhorat TH, Chou MW, Trinidad EM, et al. Chiari I Malformation Redefined: Clinical and Radiographic Findings for 364 Symptomatic Patients. Neurosurgery. 1999;44(5):1005-17. First Aid 2014 page 446.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Malformations, WBRKeyword::Chiari I malformation, WBRKeyword::Chiari II malformation, WBRKeyword::Syringomyelia, WBRKeyword::Myelomeningocele, WBRKeyword::Loss of pain and temperature, WBRKeyword::Spinothalamic tract pathway, WBRKeyword::Pain, WBRKeyword::Temperature, WBRKeyword::Cape-like distribution
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