Rhinorrhea

Stephanie A. Joe

As with many nasal symptoms, rhinorrhea is a common complaint offered by patients. Its presentation can vary widely over several different descriptive parameters, with each providing some potential information that can be used to better diagnosis its underlying cause.

Nasal Sources of Rhinorrhea

The unique anatomy of the nasal cavities with the mucosa-lined turbinates and meatus allows for maximal contact of inspired air with the mucosal surface area within a small space. The effects on inspired air include:

Temperature regulation

Humidification

Filtration

Lubrication

Odor detection

Protection against airborne pathogens

Preparation of inspired air for the lower airways

Components of the nasal lining (mucosa)

The nasal vestibule is lined with keratinized, stratified, squamous epithelium containing the vibrissae, sweat glands, and sebaceous glands.

At the mucocutaneous junction is the limen vestibule, pseudostratified respiratory epithelium that lines the entire nasal cavity and is composed of three major cell types:

— Ciliated columnar cells are the predominant cell type found in this epithelium. These cells contain cilia and microvilli that project in the mucus blanket.

— Goblet cells have a characteristic shape and lie between the columnar cells. Their cytoplasm is packed with mucus droplets extending up to the mucosal surface.

— Basal cells lie deeper in the epithelium and assist with anchoring columnar cells to the basement membrane.

The cells of the respiratory mucosa rest on a basement membrane that overlies a connective tissue layer referred to as the lamina propria.

The submucosa is thin and adherent to the periosteum and perichondrium. It contains venous plexus, blood vessels, sensory nerves, immune cells, and glands.

Glands of mucosa and submucosa

— Serous glands are located at the nasal vestibule and are a small contribution to overall mucus production.

— Seromucous glands lie in the submucosa, with ~100,000 lining the nasal cavities, where they produce most of the mucus. Their acini are either serous or mucous, with 4 to 8 times more serous acini.

— Intraepithelial glands are few in number.

Critical to mucociliary flow, cilia can number up to 100 per cell and beat 1000 times or more a minute. They are composed of microtubules in the “9 + 2” pattern, with two microtubules surrounded by nine interconnected pairs of microtubules. The nine outer pairs of microtubules are linked by dynein arms. Ciliary movement is accomplished in a biphasic pattern: a rapid phase in which cilia straighten and contact the mucous blanket, followed by the relaxation and a recovery stroke. Ciliary function can be adversely affected by pathologic processes such as inflammation or infection.

The mucous blanket

The nasal cavity produces 1 to 2 L of mucus per day.

Mucus is highly acidic (pH ~ 6.0) and contains:

— Water

— 1–2% salts

— 2– 3% glycoproteins

— Immunoglobulins

After secretion, mucus forms a bilayer consisting of a thicker, more viscous gel layer on the surface. This overlies the more serous sol layer.

Mucus is swept from posterior to anterior by cilia toward the nasal vestibule.

Autonomic control

Innervation of the nasal cavity glands and vasculature is under sympathetic and parasympathetic control.

— From the cervical sympathetic ganglion, fibers travel along the internal carotid artery and form the deep petrosal nerve. This merges with the greater superficial petrosal nerve to form the vidian nerve. This travels to the pterygopalatine fossa and contributes to the sphenopalatine ganglion. Fibers pass through without synapsing and join the second branch of the trigeminal nerve (V2) for distribution throughout the nasal mucosa.

— Parasympathetic fibers travel with the facial nerve to the geniculate ganglion. Without synapsing, the fibers exit as the greater superficial petrosal nerve. These then join with the sympathetic nerves to form the vidian nerve. These fibers synapse in the sphenopalatine ganglion and join V2 for distribution.

— Goblet cell production is at a steady rate that is independent of autonomic input.

Intracranial Source of Rhinorrhea

Cerebrospinal fluid (CSF) is continually produced to keep the total volume in an adult at ~100 to 150 mL. Its rate of formation is 350 to 500 mL/day or 20 mL/hour (or 0.35 mL/min). This total volume is turned over four or five times a day. The consistency of CSF is a thin, watery liquid that is clear and has a salty and/or metallic taste. The normal intracranial CSF pressure is ~8 to 18 cm water pressure, and the following activities increase CSF pressure: sneezing, laughing, Valsalva maneuver, rapid eye movement (REM) sleep, and orthostatic position changes (ie, from supine to sitting, pressure can increase to 40 cm water pressure).

CSF can escape into the nasal cavity and represent a source of rhinorrhea at sites of weakness or when the integrity of the skull base is breached. Sites of natural weakness include the cribriform plate, ethmoidal artery canal, optic nerve sheath, sellar diaphragm, and other congenitally weak areas of the skull base. The etiologies of skull base defect and a CSF leak are surgical dissection, external trauma, inflammatory disease, and neoplasms. CSF rhinorrhea can also be caused by CSF otorrhea draining through the eustachian tube.

Spontaneous CSF leakage associated with benign intracranial hypertension can occur. Patients are frequently middle-aged, obese, and female. Associated complaints include imbalance, pulsatile tinnitus, and pressure headaches. Radiographic evidence of empty, expanded sella has been noted in this population of patients.