A 45-year-old previously healthy man is brought to the emergency department due to acute-onset headache. It began 30 minutes ago when the patient was using the bathroom and is severe, generalized, and constant. He also has had nausea and has become progressively lethargic. The patient takes no medications. Temperature is 37.2 C (98.9 F), blood pressure is 150/90 mm Hg, pulse is 98/min, and respirations are 18/min. On physical examination, the patient appears somnolent with closed eyes. When he is instructed to open his eyes, there is obvious right-sided ptosis, and the right pupil is bigger than the left. Which of the following is the most likely diagnosis?

Question

A 45-year-old previously healthy man is brought to the emergency department due to acute-onset headache.  It began 30 minutes ago when the patient was using the bathroom and is severe, generalized, and constant.  He also has had nausea and has become progressively lethargic.  The patient takes no medications.  Temperature is 37.2 C (98.9 F), blood pressure is 150/90 mm Hg, pulse is 98/min, and respirations are 18/min.  On physical examination, the patient appears somnolent with closed eyes.  When he is instructed to open his eyes, there is obvious right-sided ptosis, and the right pupil is bigger than the left.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d541_f864_bc81_d1b56920a041_MD0003_00 This patient's sudden onset of severe headache with an associated oculomotor nerve palsy is highly suggestive of subarachnoid hemorrhage (SAH) due to a ruptured saccular aneurysm. In addition to acute-onset, severe headache, patients with SAH commonly have vomiting, photophobia, neck stiffness, and lethargy. Neurologic deficits are present in approximately 60% of patients at the time of presentation. The arterial tree at the base of the brain is in proximity to many cranial nerve (CN) origins; therefore, certain isolated CN palsies can be a sign of a compressing aneurysm in a specific location. arterial tree Oculomotor nerve (CN III) palsy can involve pupillary dilation due to loss of parasympathetic innervation, as well as ptosis and down and out eye positioning due to loss of somatic innervation. Full or partial oculomotor nerve palsy suggests an enlarging or ruptured aneurysm of the adjacent posterior communicating artery. In a similar manner, compression of the optic nerve (CN II) by an aneurysm of the internal carotid or anterior communicating artery can cause unilateral vision loss or bitemporal hemianopsia. Less commonly, a trochlear (CN IV) or abducens (CN VI) nerve palsy can result from an aneurysm affecting the superior cerebellar or anterior inferior cerebellar artery, respectively. Management of a patient with sudden-onset, severe headache and a suggestive CN palsy should involve head CT scan with angiography to evaluate for active SAH or an enlarging aneurysm with impending rupture. (Choice A) Carotid artery dissection typically presents with unilateral headache and ipsilateral Horner syndrome. Generalized headache is not typical, and pupillary dilation is not expected (Horner syndrome causes pupillary constriction). (Choice B) Cavernous sinus thrombosis generally presents with fever, headache, and periorbital swelling. In addition, there is usually palsy of CNs III, IV, and VI (all 3 nerves) resulting in ophthalmoplegia. all 3 nerves (Choice C) Cluster headache usually involves severe unilateral headache and ipsilateral signs of parasympathetic hyperactivity. Ptosis is common, but pupillary constriction (rather than dilation) is expected. (Choice D) Lateral medullary syndrome (ie, Wallenberg syndrome) results from a stroke affecting the vertebral artery or posterior inferior cerebellar artery. Patients have contralateral sensory deficits of the extremities and ipsilateral sensory deficits of the face. Sympathetic fibers may also be disrupted, resulting in Horner syndrome. Educational objective: Isolated cranial nerve palsies can be suggestive of a ruptured or enlarging saccular aneurysm with active or impending subarachnoid hemorrhage. Isolated oculomotor nerve palsy can indicate an aneurysm of the posterior communicating artery. References: Imaging of intracranial aneurysms causing isolated third cranial nerve palsy. (http://www.ncbi.nlm.nih.gov/pubmed/19726948) Evaluation of the third nerve palsy in the emergency department. (http://www.ncbi.nlm.nih.gov/pubmed/17976817)

A 45-Year-Old Previously Healthy Man Is Brought to the Emergency