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Difficulty: HardPhysical Examination Findings

A 62-year-old retired electrician with a history of poorly controlled hypertension and tobacco use arrives at the emergency department accompanied by his spouse, reporting the sudden onset of severe dizziness, unsteadiness, and difficulty swallowing that started two hours ago. Vital signs include a blood pressure of 178/102 mm Hg, heart rate of 88/min, and respiratory rate of 16/min. The patient is alert but speaks with a hoarse voice. Neurological evaluation reveals prominent horizontal nystagmus. There is a loss of pain and temperature sensation on the right side of the face and the left side of the body. Light touch, proprioception, and vibratory sensations are intact throughout. The right eye demonstrates a mildly drooping upper eyelid and a constricted pupil. Muscle strength is 5/5 in all extremities, and deep tendon reflexes are 2+ bilaterally. Based on the localization of the current neurologic deficit, which of the following additional physical examination findings is most likely to be present in this patient?

  1. Absence of the gag reflex on the right sideAnswer
  2. B
    Deviation of the tongue to the right side upon protrusion
  3. C
    Loss of vibratory and position sense on the left side of the body
  4. D
    Weakness of the right facial muscles involving only the lower quadrant
  5. E
    Inability to abduct the right eye past the midline

Answer

Absence of the gag reflex on the right side
The correct answer identifies an absent gag reflex on the right side. The clinical vignette describes a classic right-sided Lateral Medullary Syndrome (Wallenberg Syndrome), most commonly due to an occlusion of the posterior inferior cerebellar artery (PICA) or the vertebral artery. This syndrome is characterized by damage to several key structures in the lateral medulla: the vestibular nuclei (vertigo, nystagmus), the spinothalamic tract (contralateral loss of pain and temperature in the body), the spinal trigeminal nucleus (ipsilateral loss of pain and temperature in the face), descending sympathetic fibers (ipsilateral Horner syndrome), and the nucleus ambiguus. The nucleus ambiguus contains the efferent motor fibers of cranial nerves IX and X. Destruction of this nucleus results in hoarseness, dysphagia, and loss of the ipsilateral gag reflex.

Step-by-Step Solution

1
Analyze the patient's presenting symptoms and neurological examination findings.
The patient has vertigo, nystagmus, hoarseness, dysphagia, right-sided Horner syndrome (ptosis, miosis), and crossed sensory loss (loss of pain/temperature on the right face and left body).
Grouping physical examination findings is essential for anatomic localization of neurological deficits.
2
Localize the lesion within the central nervous system.
Crossed sensory findings localize the lesion to the brainstem. The combination of Horner syndrome, vestibular signs, and specific cranial nerve involvement (hoarseness from CN X) without limb weakness localizes the lesion precisely to the lateral aspect of the medulla on the right side.
Different brainstem territories control specific sensory, motor, and autonomic pathways.
3
Identify the syndrome and determine which other structures are present in the affected area.
This is right-sided Lateral Medullary (Wallenberg) Syndrome. The lateral medulla contains the nucleus ambiguus, which houses the motor cell bodies for cranial nerves IX and X.
Knowing the complete anatomical contents of the lateral medulla allows prediction of expected examination findings.
4
Select the physical exam finding associated with the affected anatomical structures.
Damage to the right nucleus ambiguus (CN IX and X) results in loss of the ipsilateral gag reflex.
The gag reflex requires an intact glossopharyngeal (afferent) and vagus (efferent) nerve arc, both of which are compromised in this condition.

Key Concept

Anatomic localization of Lateral Medullary (Wallenberg) Syndrome based on specific physical examination findings.
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Topics

Physical Examination Findings

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