Nasal emission is the audible escape of air through the nose during speech, occurring when sounds require a buildup of air pressure in the mouth. It is a common symptom indicating an issue with the mechanism that separates the oral and nasal cavities. Nasal emission significantly impacts speech clarity and articulation, often making consonants sound weak or distorted. Understanding the cause of this air escape is the first step toward improving communication.
The Mechanism of Nasal Emission
Nasal emission is fundamentally an airflow disorder occurring when the velopharyngeal mechanism fails to achieve a complete seal during speech. This mechanism is the “valve” made up of the soft palate (velum) and the pharyngeal walls of the throat. For most speech sounds requiring high air pressure, this valve must close tightly to direct all the air into the mouth.
Velopharyngeal closure is essential for sounds like /p/, /t/, /s/, or /f/, ensuring the air stays in the oral cavity to create a sharp, clear sound. When the valve does not fully close, air leaks into the nasal cavity, producing nasal emission. This rush of air is most noticeable on oral pressure consonants, which depend on that buildup of pressure.
It is important to distinguish nasal emission from hypernasality, although they often occur together. Nasal emission is the audible escape of air affecting consonant clarity (an articulation or airflow error). Hypernasality, conversely, is a resonance disorder where too much sound energy vibrates in the nasal cavity, giving the voice a “nasal” quality, particularly on vowels and voiced consonants. While both are caused by a failure of the velopharyngeal valve, one is aerodynamic (airflow) and the other is acoustic (sound resonance).
Underlying Causes of Velopharyngeal Dysfunction
Nasal emission is a direct physical consequence of velopharyngeal dysfunction (VPD), which is the faulty closing of the velopharyngeal valve. VPD is typically categorized into two primary types based on the underlying reason for the failure to close. The first is Velopharyngeal Insufficiency (VPI), which is caused by a structural or anatomical defect in the palate.
Common structural causes include a history of cleft palate, a congenital short soft palate, or a submucous cleft palate (a hidden defect beneath the oral tissue). The second type is Velopharyngeal Incompetence, which refers to poor movement of the velopharyngeal structures despite them being structurally normal. This is often due to a neurophysiological disorder, such as muscle weakness or paralysis following a stroke or due to certain neurological conditions.
Other factors can also contribute to VPD, including surgical changes, such as those following a tonsillectomy or adenoidectomy, which can affect the size of the space the velum needs to close. Sometimes, nasal emission can be a learned error, known as phoneme-specific nasal emission, where a person substitutes a sound produced in the throat for an oral sound, even if their velopharyngeal mechanism is physically sound. Determining the specific cause is necessary because it dictates whether the primary treatment will be surgical, prosthetic, or speech-based.
Identifying and Assessing Nasal Emission
Speech-Language Pathologists (SLPs) use a combination of perceptual and instrumental methods to identify and quantify nasal emission. The initial step is a perceptual assessment, where the clinician listens carefully to the person’s speech, particularly during the production of pressure-sensitive consonants. Simple, non-invasive techniques confirm air escape, such as holding a small mirror beneath the nostrils; escaping air causes the mirror to fog up.
A straw or small listening tube can also be used, with one end placed near the nostril and the other near the clinician’s ear, to amplify and better detect the sound of escaping air. For a more objective assessment, instrumental tools are employed. Nasometry measures the ratio of sound energy coming from the nasal cavity compared to the oral cavity during speech, providing a quantifiable score of nasal airflow.
More advanced visual assessments, such as nasoendoscopy or videofluoroscopy, allow the medical team to visualize the velopharyngeal mechanism in motion during speech. Nasoendoscopy involves inserting a small, flexible camera through the nose to directly observe the velum and pharyngeal walls attempting to close. These instrumental measures help determine the size, location, and consistency of the gap, which is essential for planning the appropriate intervention.
Treatment Strategies
Treatment for nasal emission is typically managed by a multidisciplinary team, focusing first on correcting the underlying velopharyngeal dysfunction. For cases of Velopharyngeal Insufficiency caused by a structural defect, surgical management is often the first line of intervention. Common surgical procedures include a pharyngeal flap, which creates a bridge of tissue to help close the gap, or a sphincter pharyngoplasty, which narrows the opening by utilizing tissue from the sides of the throat.
If surgery is not an option or is temporarily deferred, prosthetic management may be utilized to physically assist with closure. A palatal lift appliance, for example, can be used to elevate a soft palate that has poor movement, or an obturator can be used to block a persistent opening. These devices function as temporary or permanent aids to achieve the necessary seal for oral pressure sounds.
Following physical management, or for cases of Velopharyngeal Incompetence or mislearning, speech therapy becomes a primary component of treatment. Therapy focuses on teaching the person to correctly articulate sounds, often using techniques that provide visual or tactile feedback to help them redirect the airflow into the mouth. Speech therapy alone cannot correct nasal emission caused by a significant structural problem; therefore, a combination of physical intervention followed by targeted speech therapy is often necessary.