There is clear liquid flowing out of the nasal cavity, which may not be snot, but...

Author: Lv Gang, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

Reviewer: Mu Rong, Chief Physician, Peking University Third Hospital

Everyone has had a cold and had clear nasal discharge, but the clear secretions that flow out of the nasal cavity may not be nasal discharge, but cerebrospinal fluid, which is called cerebrospinal fluid rhinorrhea.

Figure 1 Original copyright image, no permission to reprint

1. What is cerebrospinal fluid rhinorrhea?

Under normal circumstances, cerebrospinal fluid will not leak into the nasal cavity.

From an anatomical point of view, the first floor is equivalent to the nasal cavity, and the second floor is equivalent to the brain cavity. There is a plate between the brain cavity and the nasal cavity, called the skull base, which is equivalent to the ceiling.

Normal brain tissue is in a mass shape, with a layer of dura mater on the outside, just like the red skin on the outside of a peanut, and the skull is like the hard shell of a peanut.

Cerebrospinal fluid is a normal brain tissue fluid that is colorless and transparent. It contains substances such as protein, sugar, chloride, etc. that nourish the brain.

Under what circumstances will cerebrospinal fluid leak into the nasal cavity?

All three anatomical structures are damaged. First, the dura mater has a tear. Second, the bone has a crack. Third, the nasal mucosa has been damaged or torn. Only when these three conditions are met can cerebrospinal fluid leak out. As long as one of the three structures is relatively intact, cerebrospinal fluid will not leak out.

Figure 2 Original copyright image, no permission to reprint

The cerebrospinal fluid is like tap water, dripping down onto a handkerchief or paper. There is a pool of water on the outside with halos and bloody stuff in the middle. The bloody stuff is not cerebrospinal fluid, but bleeding caused by injury, and the blood does not coagulate.

2. What causes cerebrospinal fluid rhinorrhoea?

The incidence of cerebrospinal fluid rhinorrhea is not very high. The most common cause is brain trauma, accounting for about 80%. Traumatic factors also include iatrogenic factors, which means that during surgery or treatment, such as craniotomy or nasal surgery, bone damage occurs, causing cerebrospinal fluid rhinorrhea.

There are three non-traumatic factors: the first is tumor; the second is congenital brain disease, such as hydrocephalus; and the third is spontaneous, when cerebrospinal fluid flows out from weak bones.

Spontaneous cerebral rhinorrhoea means that there is congenital bone weakness, and the weak places are soaked by cerebrospinal fluid, causing defective leakage. Even without trauma, iatrogenic treatment can also cause cerebrospinal fluid rhinorrhoea. For example, if a pituitary tumor grows in the pituitary fossa, the long-term compression of the pituitary tumor will cause this bone to become weak. After drug treatment, the pituitary tumor shrinks, the anatomical structure changes, and the intracranial pressure increases, so the cerebrospinal fluid flows down along the weak places.

3. What are the dangers of cerebrospinal fluid rhinorrhea?

The harm of cerebrospinal fluid rhinorrhea lies in its complications. The channels through which cerebrospinal fluid leaks, such as the pathogenic microorganisms in the nasal and oral mucosa, travel retrogradely upward through these channels to the cranial cavity, causing encephalitis and meningitis, exudation, cerebral edema, coma, and in severe cases, life-threatening.

Second, fractures after trauma can damage the olfactory nerves, causing anosmia and the inability to smell.

Third, it damages the optic nerve and causes poor eyesight.

Fourth, it causes hydrocephalus. After the cerebrospinal fluid leaks out, the normal circulation of cerebrospinal fluid is obstructed, leading to obstructive hydrocephalus.

Fifth, low intracranial pressure is the most serious. Cerebrospinal fluid leaks out, causing dizziness and headaches, and in severe cases, it can also lead to intracranial infection.

Therefore, if there is no cold or other reasons, and there is colorless and transparent liquid flowing out of the nasal cavity or the back wall of the pharynx, and it drips out of the nostrils as soon as you lower your head, just like a faucet that is not closed tightly, you should see a doctor in time to see if it is cerebrospinal fluid rhinorrhea.

At this time, the exudate needs to be tested to check the sugar content. Generally, it can be diagnosed as cerebrospinal fluid rhinorrhea only if it is above 2.7mmol/L. Normal nasal mucosal exudate, that is, nasal mucus or saliva, does not contain sugar.

4. How to treat cerebrospinal fluid rhinorrhea?

For cerebrospinal fluid rhinorrhea caused by brain trauma, we will observe the patient first, that is, provide conservative treatment, in the first two weeks because of the trauma factor.

Generally, mild cerebrospinal fluid rhinorrhea will stop leaking after one or two weeks, and the exudate will seal the leak. During this period, you should stay in bed, reduce abdominal pressure, not suck your nose or blow your nose, and use antibiotics appropriately. If conservative treatment is ineffective, surgical treatment will be adopted.

Surgical treatment is divided into transnasal surgery and craniotomy according to the surgical access.

There are two types of transnasal surgery: endoscopic treatment and single-nostril endoscopic microscopic treatment. Insert the needle into the leak, take some muscle from the thigh or the outside to plug the leak, and then cover the cut mucosa, so that there will be no leakage. This is called skull base reconstruction.

Figure 3 Original copyright image, no permission to reprint

Craniotomy is the operation that opens the hole from the top. Depending on the location and length of the leak, the doctor will decide whether to perform a bifrontal craniotomy, a unifrontal craniotomy, a transsuperciliary craniotomy, or a frontotemporal craniotomy based on the actual situation of the leak.

After the leak is repaired by surgery, most patients can be cured. Those who cannot be cured or relapse are complicated cases. For example, the leak is not a point, but a line. After this point is repaired, other places may leak again. The next leak needs to be treated.