A 30-year-old woman comes to the office due to increasing muscle weakness. The patient has not been able to grip her coffee mug or open jars due to weakness in her hands. She has also had some loss of sensation in the upper extremities that has caused her to cut herself while doing craft projects. The patient was in a motor vehicle collision 7 years ago in which she sustained a whiplash cervical spine injury. She has no other medical conditions. BMI is 22 kg/m². Physical examination reveals moderate wasting of the small muscles of the hand. Bilateral upper extremities have impaired pain and temperature sensation. Light touch, vibration, and position senses are all intact. Which of the following is the most likely diagnosis in this patient?

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11ec25c8_d5d0_2e59_bc81_aff980bdf3a8_MD0003_00 This patient has syringomyelia, a disorder caused by disruption of cerebrospinal fluid drainage from the central canal, leading to formation of a fluid-filled cavity (syrinx) that compresses the surrounding tissue. The cavity can enlarge over time and destroy adjacent portions of the spinal cord. It is most commonly seen with Arnold-Chiari type 1 malformations (extension of the cerebellar tonsils into the foramen magnum) but can also occur as a sequela of meningitis, inflammatory disorders, tumors, and trauma. Symptoms may present months to years after the initial insult. Syringomyelia can occur at any level but most commonly involves the cervical or thoracic spine, typically resulting in upper extremity symptoms. Destruction of the crossing fibers of the spinothalamic tract in the ventral white commissure results in progressive loss of pain and temperature sensation in dermatomes corresponding to the level of spinal cord involvement (sometimes called a "cape-like" distribution). Touch, vibration, and proprioception are preserved (ie, dissociated anesthesia) if the syrinx is small enough to affect only the ventral white commissure. However, expansion into the motor fibers in the ventral horns may result in progressive weakness and flaccid paralysis within the affected area. Over time, central pain, incontinence, and lower extremity manifestations may also develop. The diagnosis is confirmed by MRI, which shows an intramedullary cavity. Management usually requires surgical intervention (eg, shunt placement). intramedullary cavity (Choice A) Amyotrophic lateral sclerosis causes upper and lower motor neuron deficits with no loss of sensory function. Twitching, muscle weakness, and cramping are common symptoms. (Choice B) Cervical spondylosis is characterized by chronic degeneration of the intervertebral disks and facet joints. It usually occurs in older individuals, although it can affect younger patients with prior spine injury. Neck pain and stiffness are the most common symptoms. Cord compression may occasionally be seen but typically causes weakness below the affected spinal cord level, not regional loss of pain and temperature sensation. (Choice C) A herniated cervical disk may cause radiculopathy due to compression of the nerve root. Unilateral pain and weakness in the distribution of the involved nerve is likely, but dissociated sensory findings do not occur. (Choice D) Multiple sclerosis is a demyelinating disorder that is most common in young and middle-aged women. It presents with episodic and progressive deficits in multiple domains (eg, diplopia, focal weakness, bowel/bladder dysfunction). The white matter lesions are noncontiguous; this patient's findings are consistent with a single lesion. Educational objective: Syringomyelia is characterized by a fluid-filled cavity (syrinx) in the spinal cord that compresses the surrounding tissue. It is most commonly seen in patients with Arnold-Chiari type 1 malformations or spinal cord injury. It typically affects the crossing fibers of the spinothalamic tract in the ventral white commissure (loss of pain and temperature sensation with preserved touch, vibration, and proprioception) and may affect motor fibers in the ventral horns (flaccid paralysis). The diagnosis is confirmed by MRI, and management usually requires surgical intervention. References: Posttraumatic syringomyelia. (http://www.ncbi.nlm.nih.gov/pubmed/29262020)

A 30-Year-Old Woman Comes to the Office Due to Increasing