Learning Objectives
- Cerebral aneurysm has a variable presentation and can be a serious condition
- Asymptomatic aneurysms less than 7 mm in diameter are not treated often
- Aneurysms may be treated with surgery, interventional radiology, and occasionally medicine to prevent complications
History
A 28 year old line chef came to visit the office because of a new onset throbbing pain behind the left eye. The vision was not affected. Movement of the eyes was not affected and it did not worsen the pain. The neurological exam was normal. She had an MRI of the brain that showed no abnormalities. The patient was treated with butalbital and amitriptyline and she felt no relief. One week later, she complained that her left eye would not open and that the pain persisted. She visited the emergency room.
Examination
She has a pulse of 84 and a blood pressure of 144/86. She appears to be uncomfortable but she is alert. Her left eyelid is closed. When the eyelid is opened, her left pupil is larger than the right, and the eye cannot move medially. Her facial sensation, facial expression, shoulder shrug and tongue movement are normal. She has normal strength and reflexes. Sensation in the arms and legs is normal. She has normal finger nose finger movements and a normal gait.
Neuroanatomy and Localization
This individual has left eye ptosis, an enlarged left pupil, and weakness of left eye adduction. These functions are supplied by the oculomotor nerve on the left side. As she has normal cranial nerve function otherwise, so this lesion localizes to the oculomotor nerve. This nerve passes through the cavernous sinus, adjacent to the internal carotid artery. Malformations of this artery within the cavernous sinus commonly cause oculomotor nerve palsy. Dissection of the carotid artery more proximal to the aorta disrupts sympathetic nerve fibers, resulting in ptosis, a small pupil, but this spares eye movement (Horner’s syndrome).
Diagnosis
At the onset of this case, it is not clear that aneurysm is the problem. The patient has a new symptom that is reminiscent of a migraine headache, and there are no findings suggesting another diagnosis. Soon after, the patient develops weakness of the eyelid. This is a concerning feature that indicates a problem with the third cranial nerve, which helps move the eye inwards, controls pupil size, and helps to keep the eyelid open during wakefulness. It was reasonable for the patient to visit the emergency room in this case, because these symptoms are concerning for a cerebral aneurysm.
A cerebral aneurysm is a condition that results from the pouching or bulging of one of the arteries that supply the brain. This often happens spontaneously in the absence of trauma. It is more common in families with a history of cerebral aneurysms or in patients with high blood pressure. An aneurysm may be painful due to compression of sensory nerves or when it leaks blood, which is irritating to the surface of the brain, nerves and the meninges.
Cerebral aneurysms may be diagnosed by several kinds of studies. Noninvasive imaging is the preferred screening method. This may be either a CT angiogram or MR angiogram. These studies are normally done with contrast to show the blood better. These studies are limited because they do not show the arterial structures- just the blood. Sometimes, better resolution of the artery wall is made with a T1-fat saturated MRI sequence. This may need to be specially ordered. A cerebral angiogram is the gold standard test for aneurysm diagnosis. At some centers, it may also precede an interventional procedure.
Treatment
A cerebral aneurysm may be treated in many ways. Medical treatments are generally not effective. Sometimes control of blood pressure is important to aneurysm. Calcium channel blocking medication such as nicardipine is often used to prevent arterial vasospasm or bleeding aneurysms. Significant aneurysms should be treated surgically – either by placing a clip around the aneurysm, by removing the diseased artery, or by a catheter intervention, where debris is injected into the aneurysm, promoting the formation of blood clots which then close off the aneurysm.
There are multiple types and locations of aneurysms. A saccular aneurysm results in widening of the artery, like a swollen sausage, from side to side. These are often incidental, and rarely result in pain or damage, relative to other kinds. A berry aneurysm is more dangerous. This has the appearance of a pouching off from the artery wall, and often may have a stem. If the aneurysm becomes too large, it has a risk of spontaneous rupture, resulting in hemorrhage. It may also compress nervous tissue resulting in signs of impairment (as was the case here) or pain. Aneurysms greater than 7 mm in diameter or found to be growing in size over time are treated surgically, even if they cause no symptoms. Smaller aneurysms are treated if they have demonstrated a tendency for bleeding.
Aneurysms affecting other parts of the body are not unusual. Generally, these do not increase the risk of cerebral aneurysm. A family history of abdominal aneurysm, for example, should not increase the risk of a cerebral aneurysm. We tend to be concerned about the family risk of cerebral aneurysm if you have one and especially two or more immediate family members who have had one. For example, a parent, sibling or child is considered an immediate family member. If you have an uncle, grandparent or aunt who is affected, you should not be considered to have a significant increased risk.
Review Questions
- A patient with a headache reports to the emergency room. An MRI is ordered, which shows an incidental ACA aneurysm of 3 mm size. You confer with colleagues, who advise you to obtain a neurology consultation. You expect the consultant to tell you that:
a. there is no need for surgery
b. a calcium channel blocker medicine is indicated
c. the patient should have an angiogram procedure and possible intervention
d. only treatment of the aneurysm will resolve the headaches
e. none of the above - The patient’s sister visits her in the ER. She says that their father also had a cerebral aneurysm, and died of it age 54. She asks what her risk of having a cerebral aneurysm is. You tell her that:
a. Two close relatives are not enough to raise suspicion
b. This is a small aneurysm, and she should not be concerned
c. She should start taking a calcium channel blocker
d. She should be screened for a cerebral aneurysm
e. Her risk is very high, and she should see her doctor immediately