WBR0575
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
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| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pathophysiology |
| Sub Category | SubCategory::Neurology |
| Prompt | [[Prompt::A 36-year-old woman presents to the neurology clinic with a complaint of a 1 week history of bilateral upper extremity weakness. Upon further questioning, the patient reports that for the past 3 months, she has had multiple burns of both hands because she cannot seem to distinguish hot objects. She also reports she has numbness over the shoulders and the arms that follow a cape-like pattern. Physical examination is remarkable for burn marks in both hands, loss of pain and temperature sensation in the shoulders and arms, and diminished upper extremity reflexes bilaterally. Which of the following images depicts the location of the patient's lesion (lesion in red)?]] |
| Answer A | [[AnswerA:: ]]
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| Answer A Explanation | [[AnswerAExp::This image typically depicts spinal cord lesions of ALS that involve both descending corticospinal tracts, and the anterior horns. The involvement of both these structures is what leads to the combination of UMN and LMN symptoms seen in ALS.]] |
| Answer B | [[AnswerB:: ]]
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| Answer B Explanation | [[AnswerBExp::This image depicts isolated anterior horn injury usually seen in patients with poliomyelitis or Werdnig-Hoffman Syndrome (floppy baby syndrome). Both of these diseases only cause LMN signs due to the lack of involvement of descending motor tracts.]] |
| Answer C | [[AnswerC:: ]]
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| Answer C Explanation | AnswerCExp::This image depicts multiple, non-patterned white matter lesions usually seen in patients with multiple sclerosis. |
| Answer D | [[AnswerD:: ]]
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| Answer D Explanation | AnswerDExp::This image is depicts an expanding central canal compressing adjacent tracts typically seen in syringomyelia. The anterior white commissure is the closest structure which leads to compression of the decussating spinothalamic tracts first. |
| Answer E | [[AnswerE:: ]]
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| Answer E Explanation | [[AnswerEExp::Dorsal column lesions are not seen with syringomyelia. They are classical of tabes dorsalis in tertiary syphilis when isolated. Dorsal column lesions are also part of the subacute combined degeneration syndrome seen in vitamin B12 and vitamin E deficiency.]] |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::Syringomyelia is a disease of the spinal cord related to the development of a fluid-filled cavity (syrinx) within the central canal. As the central cavity expands, nearby spinal tracts are affected. The syrinx first interrupts the spinothalamic tract fibers that decussate at the anterior white commissure in close proximity to the central canal. Stretching of the spinothalamic fibers that relay pain and temperature results in loss of pain and temperature. Most cases of syringomyelia affect the cervical spinal cord. As a result, patients often complain of a cape-like distribution of numbness over the shoulders and the arms. In contrast, light touch, position sense, and vibration senses are usually spared because they are carried by the relatively distant dorsal columns. As the syrinx expands further, it locally interrupts neurons of the anterior horn leading to lower motor neurons symptoms of the upper extremities, such as weakness, hyporeflexia, fasciculations, and muscle atrophy. It also locally interrupts descending motor fibers leading to upper motor neuron symptoms of the lower extremities, such as rigidity and hyperreflexia. Patients typically present with a history of loss of temperature and pain sensation in the hands with a history of multiple burns. As the syrinx becomes more significant, symptoms of weakness arise. Syringomyelia can be associated with Arnold–Chiari malformation. Educational Objective: Syringomyelia is a syndrome involving a fluid filled cavity of the central canal that interrupts the spinothalamic tracts leading to bilateral loss of temperature and pain sensation usually in the upper extremities. |
| Approved | Approved::No |
| Keyword | WBRKeyword::Syringomyelia, WBRKeyword::Spinal cord, WBRKeyword::Spinothalamic tracts |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |