What is CSF rhinorrhea?
CSF rhinorrhea is a condition where cerebrospinal fluid (CSF) leaks through the nose. Normally cerebrospinal fluid is confined to the space around the brain and spinal cord. Due to its close proximity to the sinus and nasal cavity, any opening will allow CSF to leak into it and then drain out through the nose. Sometimes it can even leak out through the ears where it is then known as CSF otorrhea. Most cases of CSF rhinorrhea are due to head trauma but sometimes it occurs with surgery and other less common causes. Although it can be managed without treatment, at times surgery is needed to correct the condition. CSF rhinorrhea is not a common condition and extensive investigation should be undertaken by a doctor before assuming that any nasal discharge is cerebrospinal fluid.
CSF Rhinorrhea Reasons
Cerebrospinal fluid (CSF) is important for several functions such as :
- Acting as a shock absorber and thereby protecting the brain and spinal cord during impact.
- Keeping the brain afloat within the cranial cavity.
- Draining away large proteins and other substances that are not carried out by the veins.
The cerebrospinal fluid (CSF) is constantly circulated, with new fluid being produced and existing fluid drained. In this way some 500 to 700 milliliters of fluid are produced daily. Cerebrospinal fluid (CSF) is contained within a closed cavity to maintain its volume and therefore perform its functions. The cavity itself is made up by the bony walls of the skull (cranium) and the vertebrae of the spinal cord.
How does the CSF leak out?
Trauma can cause the bone to fracture and for CSF to leak out immediately after the injury. Normally the part of the skull where an opening forms is either structurally weak or abnormally developed from birth. At other times it have weakened during the course of life as a result of certain surgeries. However, it is possible for a severe head and face trauma to cause a fracture in an otherwise structurally intact bone. The sinus cavity may lie just beneath or in front of the bone and the CSF drains into it.
There are some instances of non-traumatic CSF rhinorrhea where the leak appears to start spontaneously with no preceding injury. There may also be no history of previous surgery that could have weakened the bone. It is believed that these cases may arise with diseases that cause the skull bone to wear down only in a specific area where the opening eventually forms. Sometimes abnormalities in the skull during fetal life and failure of some parts to close after birth may be sites which later serve as the opening for a CSF leak into the nasal cavity.
CSF Rhinorrhea Location
Most of the leaks occur in the anterior cranial fossa, the part of the cranium of the skull towards the front. Rarely does it occur in the middle or posterior (back) cranial fossa. The paranasal sinuses lying in the skull have fairly thin walls separating it from the cranial cavity where the brain is housed. A significant proportion of leaks occur in the region of the cribiform plate of the skull and into the ethmoid sinus. Other leaks arise from openings into the frontal and sphenoid sinuses. All these different paranasal sinuses empty into the nasal cavity. From here fluid drains out mainly through the nose.
CSF Rhinorrhea Causes
Injury to the head, either penetrating or closed injuries, are responsible for majority of the cases of CSF rhinorrhea. Traumatic CSF rhinorrhea can be classified as immediate or delayed.
- Immediate CSF leak occurs within 48 hours of the injury.
- Delayed CSF leak occurs within the first 3 months following the injury.
High impact injuries as seen with assault or motor vehicle accidents usually causes immediate CSF leaks.
Surgery is another form of trauma but needs to be differentiated from penetrating and closed injuries to the head. As an iatrogenic cause, the procedure is usually undertaken to treat some underlying disease. It is more likely to arise with sinus surgery (functional endoscopic sinus surgery or FESS), nasal polyp removal or neurosurgical procedures. Leaks often tend to occur within the first week after the procedure.
Spontaneous leaks may be idiopathic meaning that it arises due to an unknown cause. There is no history of surgery or trauma preceding the leak. It appears that prolonged raised intracranial pressure may be the main cause as it gradually erodes the bone and leads to a leak. In these instances the pressure is only moderately raised therefore not presenting with many other symptoms in the short term. Very high intracranial pressure is unlikely to cause a CSF leak unless there is existing bone weakness.
- Birth defects (congenital)
CSF Rhinorrhea Symptoms
The most obvious symptoms is a clear watery discharge from the nose. However, it is often missed if it does not immediately follow an injury as patients mistaken it for nasal mucus (runny nose). It can also be missed when accompanied by blood from the nose (epistaxis). The leak is usually one-sided (unilateral) although it can occur from both sides. Minor leaks may only be noticed with a change in head position as the CSF first accumulates before draining out through the nose.
There are no other significant symptoms with CSF rhinorrhea. Sense of smell is usually not affected. Headaches and disturbances in vision tend to arise with the underlying cause, like raised intracranial pressure, and not from the leak itself. Fever may be seen in meningitis. Traumatic head injury may also cause confusion, disorientation and sometimes stupor as part of a concussion.
CSF Rhinorrhea Diagnosis
Sudden or profuse nasal discharge after an accident or injury should raise the concern about a CSF leak. However, this does not conclusively indicate that the leak is CSF. A sample of the discharge should be collected and subjected to various tests which may verify that it is indeed cerebrospinal fluid. These tests include :
- Beta-trace protein
- Beta-2 transferrin
Testing the glucose content of the discharge may also help to identify cerebrospinal fluid but it is not a reliable method. Imaging studies include a CT (computed tomography) scan or MRI (magnetic resonance imaging). This may help to identify injuries and defects in the skull bone. The use of certain substances that can be injected into the CSF and highlight the movement of the fluid can assist in these imaging studies.
CSF Rhinorrhea Treatment
The treatment option depends on a history of preceding injury. Sometimes there may be no specific treatment advised apart from conservative measures. Medication may be of use in treating underlying problems or preventing complications. However, surgery is needed if other measures do not prove useful.
In a person with CSF rhinorrhea immediately after trauma, apart from surgery, the recommended approach is conservative management. Strict bed rest for 7 to 10 days with the head elevated may be sufficient for the leak to resolve. Many patients with a CSF rhinorrhea become very concerned upon hearing that the nasal discharge is “brain fluid” (cerebrospinal fluid). Conservative management may appear to patients as if there is no decisive medical or surgical measures being undertaken. However, bed rest with simple measures to avoid coughing, sneezing and straining during bowel movement may achieve the desired result very effectively.
The use of medication is of limited use except in a case of raised intracranial pressure. Diuretics, commonly known as “water pills”, may help reduce the fluid volume in the body and therefore the CSF volume. Antibiotics may be needed for treating bacterial meningitis. It is also prescribed as a preventative measure against meningitis as microbes from the nasal cavity may be able to enter and infect the otherwise sterile cranial cavity.
Surgical measures are aimed at identifying the exact site of the leak and plugging it. A graft uses a piece of bone and special “glue” to plug the leak. Endoscopic procedures are preferable as it less likely to be associated with complications and has a success rate of over 90%. Penetrating injuries to the head may require more extensive surgery to close the wound. Recurrence of a CSF leak is not uncommon but this is largely dependent on the cause and any underlying defects in the bone.