A 6-year-old girl with Down syndrome is brought to the clinic due to behavioral changes. Over the past month, she has stopped running, tripped frequently while walking, and accidentally knocked toys over more often than normal. The patient was toilet-trained at age 4, but recently she began having frequent urinary accidents while playing and has started wearing a diaper again. Physical examination shows an ataxic gait. Muscle tone is decreased throughout. Bilateral ankle deep tendon reflexes are hyperreflexic. When the soles of the feet are firmly stroked, the big toes move upward and the other toes fan out. Urinalysis is normal. Which of the following is the most likely cause of this patient's presentation?

Question

A 6-year-old girl with Down syndrome is brought to the clinic due to behavioral changes.  Over the past month, she has stopped running, tripped frequently while walking, and accidentally knocked toys over more often than normal.  The patient was toilet-trained at age 4, but recently she began having frequent urinary accidents while playing and has started wearing a diaper again.  Physical examination shows an ataxic gait.  Muscle tone is decreased throughout.  Bilateral ankle deep tendon reflexes are hyperreflexic.  When the soles of the feet are firmly stroked, the big toes move upward and the other toes fan out.  Urinalysis is normal.  Which of the following is the most likely cause of this patient's presentation?

Quizplus · Accepted Answer

11ec25c8_d738_bfa6_bc81_cd3598f4d1c8_MD0003_00 Atlantoaxial instability is seen in >10% of patients with Down syndrome. Excessive laxity in the posterior transverse ligament increases mobility between the atlas (C1) and the axis (C2). Although most patients are asymptomatic, symptoms can develop due to compression of the spinal cord. Down syndrome Presentation can include weakness, gait changes, urinary/fecal incontinence, and vertebrobasilar symptoms such as dizziness, vertigo, imbalance, and diplopia. On examination, upper motor neuron findings such as spasticity, hyperreflexia, and a Babinski sign (ie, upgoing big toe) are often present. Patients with Down syndrome are normally hypotonic; symptomatic atlantoaxial instability may have no effect on the low tone or cause hypertonicity. Diagnosis is confirmed with lateral x-rays of the cervical spine in flexion, extension, and in a neutral position. Open-mouth x-rays can also be helpful in visualizing the odontoid. Treatment is surgical fusion of C1 to C2. (Choice A) Although there is a higher prevalence of Alzheimer disease among individuals with Down syndrome, it usually presents around age 40-50. (Choice C) The risk of hypothyroidism is increased in individuals with Down syndrome. These patients can experience decreased growth velocity, weight gain, cold intolerance, fatigue, constipation, or declining school performance. Neurologic manifestations can include delayed reflexes, but upper motor neuron signs do not occur. (Choice D) Spinal cord infarction presents with acute onset of severe pain, weakness, and paresthesias. This condition is rare and more common in adults, and there is no increased risk in patients with Down syndrome. (Choice E) Tethered cord syndrome can cause weakness, decreased sensation, urinary incontinence, and hyporeflexia. Because the spinal cord is affected below T12/L1, upper motor neuron findings are not seen. Tethered cord syndrome is commonly associated with spina bifida, not Down syndrome. Educational objective: Patients with Down syndrome are at increased risk of atlantoaxial instability. When symptomatic, atlantoaxial instability can present with upper motor neuron findings, urinary/fecal incontinence, gait changes, or weakness. References: Prevalence of atlanto-occipital and atlantoaxial instability in adults with Down syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/24530459)

A 6-Year-Old Girl with Down Syndrome Is Brought to the Clinic