90% of headaches in pregnancy are migraine or tension-type headaches.
Unfortunately, pregnancy is also a time of risk for two serious causes – cerebral sinus thrombosis and idiopathic intracranial hypertension (which is often eventually diagnosed as cerebral venous thrombosis).
How should the fact the patient is in the third trimester affect our management and investigations for headache? This is a problem that I had to deal with in the triage unit of our hospital maternity unit.
A 36 year old woman is 31+6 weeks into her third uncomplicated pregnancy. Her first two pregnancies were unremarkable. For the past 4 days she has complained of a new headache. The headache is bilateral and frontal. There are no neurological symptoms or signs. The headache is episodic lasting minutes at a time and relieved by paracetamol within 30 minutes. It is not worsened by lying flat or coughing. There is no photophobia or neck stiffness. She is otherwise well.
On examination, there is no neurological deficit. There is no papillodema.
Is an MR venogram indicated for possible venous sinous thrombosis because this is a new onset headache in the last trimester of pregnancy? Or is this a classic tension headache and needs nothing more than reassurance and red flag safety netting?
If we decide even this presentation requires an MR venogram, then it seems pretty much any third trimester woman with a headache will merit a serious discussion over MR venogram.
I decided to trawl the evidence to see what information from the history and examination can help select the right patients for MR venogram.
From the history
Wassey et all looked at 200 people with confirmed cerebral venous thrombosis to see which features were predictive.
68% of the patients had complained of some sort of headache.
60% of the headaches were acute (1-3 days).
24% were subacute (4-14 days).
10% were chronic (more than 14 days).
The nature of the headache when described was throbbing (9%), band like (20%), thunderclap (5%) or other (pounding, exploding, stabbing, etc.) (20%).
32% of patients had a normal neurological examination. Papilloedema was only present in 15% of cases.
So what features should make me think CVT?
Symptoms can range from a thunderclap headache to a chronic progressive headache over weeks. About a tenth of cases have no headache. Between a quarter and a third of cases have no neurology signs or symptoms. Basically, there is no ‘classic history’.
However, all is not lost. There are some features which do matter:
- Headache is the most common symptom in CVT. It is often indicative of raised ICP (i.e. worse on lying flat, on sneezing etc.)
- The headache of CVT is typically described as diffuse and often progresses in severity over days to weeks.
- An isolated sixth nerve palsy always needs work up for raised intracranial hypertension.
- Seizures are particularly common in pregnancy associated CVT.
- Bilateral focal neurological signs could be from a cerebral venous thrombosis but would rarely occur from an arterial problem.
How bad is pregnancy for CVT?
Incidence estimates for CVT during pregnancy and the puerperium range from 1 in 2500 deliveries to 1 in 10000 deliveries in Western countries, and ORs range from 1.3 to 13. The greatest risk periods for CVT include the third trimester and the first 4 postpartum weeks.
Selecting the right patients
Factors that may suggest the diagnosis, and thus prompt imaging evaluation, include:
- a new, atypical headache
- headache that progresses steadily over days to weeks despite conservative treatment
- thunderclap headache.
In addition, a greater level of clinical suspicion for CVT should be maintained in patients with a hypercoagulable state.
Which imaging for a pregnant lady?
MR venogram is ideal. According to iRefer: “Imaging plays a primary role in the diagnosis of cerebral venous sinus thrombosis. MRI or CT can demonstrate venous infarction and other complications but MR or CT venography will usually be required to confirm venous sinus thrombosis.”
From http://www.rcog.org.uk/news/tog-release-healthcare-professionals-must-be-aware-signs-symptoms-and-appropriate-response-rare : Imaging of the brain should never be withheld because a woman is pregnant and women should be reassured that imaging is safe.
So what is your strategy for the above lady?
Super strong reasons for CVT imaging (I would request MRV)
Focal neurology esp papillodema and/or sixth nerve palsy
Altered mental status
Previous history of unprovoked thrombosis (the strongest risk factor of all for thrombosis generally)
Other major risk factor e.g. recent surgery, systemic infection, hypovolemia from postpartum haemorrhage etc.
Raised ICP features
Thunderclap headache (after ruling out other causes)
Decent reason for CVT imaging (i.e. I would more often than not request an MRV)
Progressive headache over days despite conservative treatment and none of the above
What do you think?