So let's learn a little bit more about low pressure headaches.
Low pressure headaches occur as a result of reduced CSF production
or CFS loss from a spiral neural tear or a lumbar puncture
and a post-LP headache is a classic presentation of a low pressure headache syndrome.
Low pressure headaches have an annual incidence of 5 per 100,000.
There's a slight female to male predominance 2 to 1 ratio of female to males presenting with this presentation.
There's a prominent positional component and I cannot underscore this enough,
that's how you diagnose this.
On history, really finding a patient whose symptoms are relieved by lying down
and when they stood up this induces the headache, this brings the headache on and exacerbates it.
This requires evaluation for cause and specific treatment,
and so it's important to ask those questions when we're evaluating patients.
This is one of those key questions we ask to all headache patients,
is your headache brought on by sitting up?
And here we see a schematic of the normal CSF flow.
CSF begins in the lateral ventricles, drains into the third ventricle through the cerebral aqueduct
to the forth ventricle down the central spinal canal,
then around in the lumbar cistern and back up, eventually, up to the arachnoid granulations.
Low CSF headaches come from reduced production in the lateral ventricles
which is extremely rare, and then more commonly,
we can see CFS leak as a result of a tear in the dura along the spine from arthritis
or other degenerative changes that can cause this, this headache syndrome.
What are the symptoms of a low pressure headache?
The pain is often bifrontal or a frontal predominance,
but many headaches present with this frontal predominance of head pain.
Here we can see an association with nausea, dizziness, or spots in the vision,
muffled sound or hearing, and again, those symptoms can be seen in many headache syndromes.
The key thing for low pressure headaches is the positional component,
worse with sitting up or really initiated, the headache is brought on by sitting up
and improved with lying down or lying flat.
Rarely we can see some other physical exam findings.
We can see diplopia from cranial nerve VI palsy.
In severe cases, is a result of loss of CSF, the brain sags
and when the brain sags down it can compress the VI nerves
as they're coursing out from brain stem to the, to the face
and this can result in cranial nerve VI palsy,
so that's something to investigate in these patients.
This can also be seen in high pressure headaches
where the high pressure also pushes the brain inferiorly.
Galactorrhea can be seen from pituitary stalk compression.
Again, as the brain sags, the pituitary can become compressed
and we can see a stalk effect or frank compression
that can present with endocrinologic abnormalities and potentially galactorrhea.
So these are rare to be seen, they're seen in more severe cases,
but important things to evaluate on the exams
or think about in clinical vignettes for these patients.
What are some of the causes of low pressure headaches?
Post-lumbar puncture, that's the most common cause.
We see it in about 25% of patients who undergo an LP.
Headache after LP is extremely common and the vast majority of patients,
it will resolve spontaneously within about five to seven days.
Patients whose pain continues after five to seven days have post-LP headache or severe,
more severe or moderate to severe, post-LP headache and should undergo treatment.
CSF over-draining in patients who have a shunt and that shunt is draining CSF
as a result of any cause over-draining of CSF can cause a low pressure headache,
and we would reduce the amount of CSF that the shunt is draining.
Traumatic CSF leak is an iatrogenic cause and a healthcare induced
cause of low pressure headache.
We can see this with cranial surgery, we can also see it with trauma,
trauma affecting the mastoid air cells can result in otorrhea or CSF coming out of the ear,
or in the frontal sinuses, we can see rhinorrhea or CSF draining out of the nose or nares,
and this can indicate a CSF leak which requires surgical management.
Spontaneous CSF leaks can also be seen
and we typically associate that with a tear in the dura often along the spine
in patients with degenerative spinal disease,
and that CSF tear results in leaking of the CSF and intracranial hypotension or reduced CSF.
This is associated also with connective tissue disorders,
Marfan syndrome and meningeal diverticulum, which would be rare.
And in very rare, uncommon cases we can see low CFS intracranial hypotension with severe hypovolemia.
This is extremely rare and I would remember the first four categories
and causes of intracranial hypotension.
How do we evaluate these patients?
Well, if we do a spinal tap, we should see a low opening pressure,
there is low pressure, intracranial hypotension,
and typically, we define low pressure as less than four centimeters of water on a spinal tap.
But imaging, is really the best way of evaluating these patients.
It's the non-invasive method of assessing this potential ideology.
This would be done with brain MRI with and without contrast,
and there are a number of findings that we can see, diffuse pachymeningeal enhancement,
the center sagging of the brain, subdural hematomas or hygromas and empty sella.
Here, in the green arrow, we see sagging of the corpus callosum;
the blue we see sagging of the occipital lobes; the yellow is cerebellar tonsillar ectopia,
the cerebellar tonsils, that lower part of the cerebellum is pulled down,
dragged down as a result of low pressure in the CSF space;
as well as dragging down, drawing down of the optic chiasm
which we see in red here, so there's just less fluid and less buoyancy of the brain
and the brain sags.
Additional studies that can be done include CT myelography to identify the site of CSF leak.
This is where we inject a radiotracer and with CT, we light up the CSF space
and we're looking for signs of CSF exiting the dural sleeve,
exiting the nerve roots as a result of a dural tear which would be repaired surgically.
And then MRI of the spine with and without contrast,
can be used to evaluate also a site of CSF leak
and it's really favored these days over CT myelography.
So to review some of the many MRI findings that can be seen in intracranial hypotension,
this is a laundry list and we'll talk about the mnemonic that can help us to understand these.
I think it's important to understand the many things that can be seen,
this is frequently none invasively diagnosed by imaging,
with the clinical history and the imaging being used to establish this diagnosis,
so it's important to be aware of these things.
We can see diffuse pachymeningeal enhancement, just like in the case presented here.
It may look like an infectious process or a carcinomatous process,
but that smooth enhancement, all over symmetrically throughout the brain,
really is more suggestive of intracranial hypotension
particularly in the appropriate clinical setting.
We can see the center sagging of the brain
and we saw that on the most resent MRI that we discussed. Descent of the cerebellar tonsils,
descent of the brainstem, distortion of the anterior-posterior diameter of the brain stem
or flattening of the pons as the midbrain and pons descend downward
with the sagging of the brain.
Descent of the opening of the aqueduct below the incisural line,
obliteration of some of the basal cisterns, the brain is being pulled down.
We can see descent or sagging of the other parts of the brain,
crowding of the posterior fossa, flattening of the optic chiasm.
In addition, we can see subdural fluid collections
and sometimes these patients present with headache,
and a CT scan shows subdural collections,
and we think, initially, clinicians may be concerned that the subdurals may be causing the head pain,
until the rest of the constellation of findings supports
that the subdurals are secondary to intracranial hypotension.
Engorgement or enlargement of the pituitary, engorgement of the cerebral venous sinuses,
decrease in the size of the ventricle, I mean there's a laundry list of things
that we can see on imaging that would point us in this direction.
So how can we remember those?
Well, first, let's talk about the mechanisms of these MRI abnormalities,
why are they happening? What's occurring?
Well, the final common process is CSF hypovolemia.
Intracranial hypotension, less fluid in the CFS space.
And there's three things that are contributing to that finding.
One is CSF volume compensations as a result of reduced CSF volume.
Other parts the brain in the skull complex take over for that and compensate for that reduction in volume.
This is where the subdural fluid collections are from,
these are secondary subdural fluid collections that are taking up the space
that's left over from where the CSF once was.
We also see engorgement of the epidural venous plexus.
Engorgement of the veins is accommodating compensation compensating
for the reduction in CSF volume.
And venous hyperemia, meningeal hyperemia
that results in defuse pachymeningeal enhancement.
Pituitary venous hyperemia that relates to pituitary enlargement
and enlargement of the cerebral venous sinuses that presents
with engorgement of cerebral venous sinuses.
There's sinking of the brain which results in the characteristics findings that we talked about,
descent to the cerebellar tonsils, decrease in the size of the subarachnoid cisterns
and flattening of the optic chiasm, as well as ventricular collapse.
There are no ventricles, slit ventricles, small ventricles both in the lateral ventricles
and in the descending CSF spaces.
How can we remember this? That's a lot of things.
What's a quick easy way at the bedside or with the clinical vignette
to remember the MRI findings that supported diagnoses of intracranial hypotension?
Well, I think, CSF SEEPS in low pressure headaches,
and that stands for, subdural fluid collection, enhancement of the pachymeninges,
and those are two really important findings. Engorgement of the venous sinuses,
the venous sinuses are enlarged. Pituitary enlargement and sagging of the brain.
We should think about those SEEPS findings in patients
who presents with prominent positional headache.
What about treatment? How do we treat these patients with intracranial hypotension?
How do we get extra fluid back in to that CSF space?
Well, for patients who have post-lumbar puncture headache,
the first treatment is aggressive oral hydration
and we encourage this for any patient who undergoes a lumbar puncture.
Drink a lot of fluid and lay flat immediately after that procedure,
then that adds just has a little bit of extra fluid into the CSF space
and prevents a prolonged leaking or persistent leaking out of that dural puncture.
We liberalize caffeine intake during the first several days for patients
who have persistent headache.
Caffeine has been shown to increase CSF production,
so for dealing with the CSF leakage we want to increase production of CSF
to accommodate that and caffeine can be one way to do that.
And ultimately, for patients who failed those conservative measures,
five to seven days following their lumbar puncture
and have persistent positional headache, we would consider an epidural blood patch.
Here you can see the procedure for performing both the lumbar puncture
and an epidural blood patch.
For the blood patch, we take a small amount of blood and we insert the needle
and blood into that epidural venous plexus,
not necessarily at the sight of the lumbar puncture,
but anywhere in that area with the hope and anticipation that that will clot up that CSF leak,
and this can be a very successful procedure.
The first epidural blood patch is not always successful,
and in patients who continue to have persistent symptoms,
we would consider multiple blood patches
which are usually successful for patients with post-LP headache.
What about patients with spontaneous intracranial hypotension
either because of a spinal dural tear or some other cause?
In these patients, we would also consider a blood patch.
We can't increase CSF production forever,
and so ultimately, the best treatment is to block up that sight of CSF leak,
and some patients may require surgical correction.
If there's an area of dural tear in the spinal cord that is persistent
and fails blood patching, then surgical correction is the treatment of choice.