Velopharyngeal Insufficiency

Etiology

VPI may result from incomplete closure of the velopharyngeal sphincter, which controls the airflow into the nasal cavity during speech and prevents nasal regurgitation during swallowing. VPI can occur secondary to structural deficits, neurological disorders, faulty learning, or as a syndromic finding.[2][3]  

1. Structural: The velopharyngeal sphincter may fail to obtain a seal secondary to a cleft palate (overt or submucosal), congenital short soft palate, nasopharyngeal disproportion, poor sphincter mobility from tonsillar hypertrophy, or scarring from prior surgery.[4] Iatrogenic causes such as cleft palate repair can cause or worsen VPI through poor mobility of the soft palate due to surgical scarring, misalignment of the levator veli palatini muscles, or the creation of a palatal fistula. Adenoidectomy can enlarge the velopharyngeal port so much that it prevents adequate closure.[5][6]
2. Neuromuscular: Neurologic or musculoskeletal injury may result in incompetent closure of an anatomically-sound velopharyngeal sphincter. Causes include head trauma, stroke, cerebral palsy, myopathy, muscular dystrophy, neuropathy, or progressive degeneration of the pharyngeal plexus secondary to Amyotrophic Lateral Sclerosis, Parkinson’s disease, Mobius syndrome, or Trisomy 21 syndrome.[7][8][9] VPI can result if the head and neck muscles are involved, especially the VP musculature. Myasthenia Gravis is an autoimmune disease that causes atrophy of skeletal muscles by targeting the acetylcholine receptor involved in neuromuscular signal transmission. Functions such as swallowing, phonation, and gaze fixation are impaired, resulting in hoarseness, diplopia, dysphonia, eyelid ptosis, and poor head stabilization. Cerebral palsy may be associated with hypotonia and gross motor weakness.[3]
3. Developmental/faulty learning: Children can learn and emulate poor pronunciation, articulation, or dialectical influences and masquerade as VPI. VPI may also arise from compensatory mechanisms after cleft palate repair. This includes greater use of nasal sounds (n, m, ng), glides (w, j), voiceless stops (p, t, k), voiceless fricatives (f, s), facial grimacing, and fewer plosives.[10] Differentiating between VPI and articulation disorders is challenging and best done by a speech-language pathologist experienced in cleft speech abnormalities. Faulty learning is best corrected by speech therapy rather than surgery.
4. Pediatric syndromes: VPI may be an associated symptom for many syndromes, including trisomy 21, Klippel-Feil, epidermal nevus syndrome, Turner syndrome, and VATER.[11] Velocardiofacial syndrome (VCFS) or 22q11 Deletion Syndrome is one of the most common syndromic causes of VPI in noncleft patients and affects 1:2000 to 1:4000 newborns.[12][13] Anomalous neural crest migration disrupts the development of the pharyngeal arches.[14][15] These patients present with dysmorphic facies, conotruncal cardiac defects, hypocalcemic hypoparathyroidism, T-cell mediated immune deficiency and variable neuromuscular weakness of the palatal and pharyngeal muscles. They may also have structural palate deformities such as reduced muscular volume, submucous cleft palate, and complete cleft palate.[16] The disorder may arise sporadically or in an autosomal dominant fashion. Approximately 27% to 92% of VCFS children have VPI, speech delay, feeding problems, and speech/language delay.[3][15]

Epidemiology

An overt cleft palate occurs in approximately 1 in 650 to 750 children born annually and is the most common cause of VPI.[3] Following primary cleft palate surgery, a deficiency persists in up to 20% to 30% of patients.[17] VPI can also be a complication after oral surgery. The incidence of VPI after adenoidectomy ranges from 1 in 1,500 to 1 in 10,000.[18][19] Postoperative palatal fistula and VPI occur after primary cleft palate repair at a rate of 3.4% to 15%.[20][21]

The most common diagnosis in patients with VPI of unknown cause is 22q11.2 deletion syndrome.[22] The frequency of 22q11 deletion syndrome ranges from 1 in 2000 to 4000 [12][13], with 27% to 92% of diagnosed children having VPI.[15]

Pathophysiology

The velopharyngeal sphincter consists of the soft palate (velum), levator veli palatini, tensor veli palatini, palatopharyngeus, palatoglossus, muscularis uvulae, and the superior constrictor muscles.[3] During normal velopharyngeal closure, the levator veli palatini contracts the velum posterior-superiorly, while the lateral pharyngeal walls and posterior pharyngeal wall contract medially and anteriorly, respectively. This closes the velopharyngeal port and separates the nasal and oral cavities during speech, swallowing, vomiting, blowing, and sucking.

During normal speech, this separation allows airflow to be channeled from the vocal cords to the oral cavity's articulating tongue, lips, and teeth. This produces the consonants (p, b, t, d, k, g, f, v, s, z, sh, ch, ge, l, r, w, y) and vowel sounds or phonemes.[23] A phoneme is the smallest unit of sound that distinguishes one word from another (ie, the t in “bat” vs. “bag”). Furthermore, air pressure needs to build up to 5 to 7 mm Hg in the oral cavity to produce oral plosives, fricatives, and affricatives.[3] Plosives are consonant sounds created when air is stopped completely in the oral cavity and then suddenly explodes with its release, such as the “p” sound. Fricatives are consonant sounds created by narrowing the airflow, such as the “s” sound. Affricatives are plosives followed by a fricative, such as the “ch” sound. Phonemes can be divided into voiced versus voiceless, depending on whether the vocal cords also resonate. The soft palate is relaxed, and the nasal and oral cavities are coupled only for 3 nasal consonant sounds in English (m, n, ng).[24][23] Partition of the 2 cavities also prevents nasal regurgitation of liquids and solids during swallowing and provides adequate negative pressure in the oral cavity during sucking.

During VPI, airflow leaks into the nasal cavity secondary to anatomic, neurologic, or functional impairment. The sound produced at the vocal cords subsequently enters both the oral and nasal cavities, causing both cavities to resonate and create an overall “nasal” sound due to excessive nasal airflow. This is also known as nasal emission or nasal escape.[3][23] In severe cases, a small stricture in the nasopharynx can create a distinct, fricative sound, termed nasal turbulence.[23]

Patients’ ability to produce consonant sounds becomes impaired,d and they may develop maladaptive compensatory mechanisms such as glottal stops, pharyngeal fricatives, and facial grimaces to close the anterior nares and decrease nasal airflow.[4][25] Those with mild VPI may compensate for decreased oral air pressure by increasing overall laryngeal airflow and shouting to produce normal speech volume. This may eventually lead to voice hoarseness and vocal cord nodules. VPI results in decreased speech intelligibility and significant functional and social impairment.[4]

History and Physical

A detailed history should include any diagnosed syndromes, history of cleft palate, history of recurrent ear infections, neurologic abnormalities, prior surgical intervention within the oral cavity or pharynx, episodes of nasal regurgitation during eating, and risk for obstructive sleep apnea.[3][24] 

The physical examination should focus on the oral and nasal cavities with attention to the soft palate height, mobility, symmetry, tonsil size, tongue mobility and symmetry, oral competence, nasal mucosa, nasal turbinates, and septum. Inspection for anatomical abnormalities such as a submucosal cleft palate, bifid uvula, zona pellucida, posterior palatal notching, or neuromuscular weakness and asymmetry is recommended. Mobility of the soft palate is inspected by asking the patient to maintain a sustained phonation of the vowel sounds “e” or “i.” The clinician should also perform an otoscopic exam to assess for otitis media with effusion or tympanic membrane retraction, as VPI can be associated with Eustachian tube dysfunction.[3][24]

Evaluation

The diagnosis of VPI is obtained through history, physical exam, assessment of speech production, imaging, and instrumental evaluation.   

Instrumental assessment provides a visual complement to perceptual speech analysis. It is performed with either video-nasal endoscopy or multiview videofluoroscopy by an interdisciplinary team of otolaryngologists, speech pathologists, and radiologists.

Perceptual speech analysis is the gold standard for VPI diagnosis and is performed by a speech-language pathologist (SLP). Patients are asked to produce plosive, fricative, and affricative sounds and assessed for hypernasal speech, compensatory facial grimacing, or misarticulation. Common phrases include “pet the puppies” and “Kathy kissed the ca.”. Patients can also be asked to count from 60 to 80. A dental mirror can be placed under the nostrils to visualize any nasal air emission through the fogging of the mirror.[3][26]

Video-nasal endoscopy uses a pediatric flexible laryngoscope to directly visualize the nasal passages, nasopharynx, adenoids, and soft palate. Live images are displayed on a video monitor for the speech pathologist performing the phonemic evaluation on the patient. The velopharyngeal sphincter is assessed during sucking through a straw and during the production of plosives, fricatives, and affricatives. The location of VP closure, size of VP gap, and mobility of VP structures can be visualized and used to guide surgical decision-making. Nasal endoscopy can also diagnose an occult cleft palate, seen as a midline groove on the nasal surface of the soft palate, as the cause of a patient’s VPI.[3]

Multiview videofluoroscopy is commonly used in young children who may not tolerate a video-nasal endoscopy. Barium is given transnasally to coat the lateral and posterior pharyngeal walls of the soft palate. Serial images oriented in the lateral, frontal, and basal views are taken to assess VP closure during phonemic evaluation by the speech pathologist. The VP closure pattern is then classified as coronal, sagittal, or circular (symmetric). Coronal closure involves only the posterior pharyngeal wall and soft palate. Sagittal closure involves only the lateral pharyngeal walls. Circular closure involves all structures equally.[3][24]

Cephalometrics use serial x-rays from multiple views to study VP anatomic relationships during sustained speech. The anterior insertion of the levator veli palatini muscle into the soft palate is assessed, with more anterior insertion (seen in occult cleft palates) resulting in decreased soft tissue stretch and a VP gap during speech. Abnormalities in the cervical spine or skull base (platybasia) can contribute to nasopharyngeal disproportion. Cephalometrics is a quantifiable and reliable evaluation for treatment planning in children with velocardiofacial syndrome and isolated cleft palates.[3][27]

MRI can be used to assess levator veli palatine muscle size, insertion into the soft palate, and orientation for cases of suspected submucosal or occult clefts.[28] Advantages include non-invasiveness, high-quality imaging, and lack of radiation exposure. However, it is expensive and often requires sedation for young children.[3]

Nasometry measures nasal emission and calculates a ratio between nasal and oral sound emissions (nasalance) using a sound separator placed between the nose and upper lip. The ratio is compared with normative values. Preoperative and postoperative nasalance can also be compared to determine surgery success. However, nasometry does not localize or quantify the VP gap. Large VP gaps can produce artificially low nasometric scores due to diminished high-pressure airflow.[3][24]

Treatment / Management

Treatment modalities for VPI include speech therapy, prosthetics, and surgery.[23]

Speech therapy is the mainstay of treatment for patients with mislearned articulation and those with poor compensatory mechanisms from VPI. In addition, patients who undergo surgical intervention should continue speech therapy to enhance their speech outcomes further.[24]

Oral prosthetics are custom-made by prosthodontists and anchored to the maxillary teeth to elevate the soft palate. They are usually poorly tolerated by patients and often used as a temporary measure or for poor surgical candidates.[24] Prosthetics may also be utilized for patients with large palate fistulas after surgery or as a temporary measure during a staged palate repair before completion of the second stage.

Surgery is the definitive treatment for anatomic causes of VPI to create a functional seal between the nasal and oral cavities while avoiding airway obstruction. Operative repair usually occurs after 3 to 4 years of age when patients cooperate with instrumental diagnosis.[3] Surgical interventions include palate muscle repositioning, pharyngeal flap, sphincter pharyngoplasty, and posterior pharyngeal wall augmentation.[3][4](A1)

Palatal muscle repositioning maneuvers lengthen or readjust the orientation of palatal muscles. The Furlow double-opposing Z-plasty was originally used for primary cleft palate repair but had the added benefit of lengthening the palate by reorienting the levator veli palatini muscles transversely.[29][30][31] It also has a lower risk of causing obstructive sleep apnea compared to the sphincter pharyngoplasty and pharyngeal flap.[32] Intravelar veloplasty involves realigning the levator veli palatini for cleft palate patients who underwent inadequate muscle correction after their primary palate repair. The soft palate is opened along the midline with meticulous dissection and realignment of the abnormally inserted muscles.[4][20] Buccal myomucosal flaps raised from the inner aspect of the cheek have also allowed the lengthening of the velum and retroposition of palate muscles.[33][34][35](A1)

Pharyngeal flap is ideal for the sagittal closure pattern. It involves elevating a midline, superiorly-based mucosa flap, and superior pharyngeal constrictor muscle from the posterior pharyngeal wall and suturing it to the posterior soft palate.[36][37] The flap narrows the nasopharyngeal inlet and creates 2 lateral ports for nasal airflow, which can seal the bilateral medial movement of the lateral pharyngeal walls. The width of the midline flap is determined based on the VP gap, location of VP closure, and mobility of the lateral pharyngeal walls on pre-operative nasal endoscopy.[38][39] The pharyngeal flap is also effective in some patients with neurogenic causes of VPI, such as those with 22q11 deletion syndrome and poor palate movement. Because it involves the creation of a permanent bridge of tissue between the palate and the posterior pharyngeal wall, it is not as physiologic as some of the other options for closure.

Sphincter pharyngoplasty is ideal for the coronal closure pattern and involves elevating bilateral, superiorly-based palatopharyngeal mucosa and muscle flaps. The flaps are rotated 90 degrees, and the distal ends are sutured to the contralateral posterior pharyngeal wall or to each other to create 2 horizontally overlapping arms.[40][41] This creates a smaller central port and a shorter transverse distance between the soft palate and posterior pharyngeal wall.[42]

Posterior pharyngeal wall augmentation involves expanding the posterior pharyngeal wall with a graft or alloplastic material to decrease the distance between itself and the soft palate. Several materials have been described, such as cartilage, fascia, acellular dermis, calcium hydroxylapatite, hyaluronic acid, fat, and silicone.[1][24][43] This surgical approach is best suited for mild VPI with a small central gap and can complement pharyngoplasty where a small gap persists.[4][24](A1)

Differential Diagnosis

Faulty learning or dialectal influence. Children with no anatomical or neurological disorders may present with mild hypernasality secondary to mislearning or exaggerated regional dialects emphasizing nasal characteristics.[10] Speech therapists should consider the native language and dialect of patients when performing perceptual speech analysis. There is no distinction between nasal and oral vowel sounds in English, but distinctive nasal vowel sounds are familiar in many other languages, including French, Portuguese, and Polish.

Speech Sound Disorder (SSD) is a broad speech impediment where patients cannot correctly form sounds of certain words. Children commonly try to substitute, omit, or change the sounds of specific phonemes, resulting in unintelligible speech. Although this is frequently seen in young children, most kids self-correct their speech by 4 years of age. SSD can be divided into articulation disorders, which involve a deficit in the motor production of sound, and phonologic disorders, characterized by trouble learning the different speech sounds and recognizing their distinct meanings.[44] Treatment is with speech therapy if the child does not self-correct before school age.

Childhood apraxia of speech (CAS) is a rare neurological condition that impedes a child’s ability to produce sound precisely and consistently. It involves a deficit in motor programming and planning, and children cannot express what they want to say in the necessary fine oral-motor movements. They have inconsistent errors in consonant and vowel production when repeating sentences.[45] These children need intensive and individualized treatment plans involving both an experienced speech-language pathologist as well as the child’s caregivers.

Tonsillar hypertrophy can restrict VP closure and cause VPI. Symptoms can be improved after tonsillectomy. Evaluation and treatment of tonsillar hypertrophy should occur before any surgical interventions for VPI, as pharyngoplasty in the setting of tonsillar hypertrophy can further obstruct the airway.[24]

Treatment Planning

Due to the varying etiological causes of VPI, a thorough evaluation must first be performed. Patients with hypernasal speech secondary to faulty learning, phonologic disorder, or language impairment without anatomic or neurological deficits should be treated with speech therapy.

Instrumentation can assist in surgical planning by determining the location of the VP closure, size of the VP gap, mobility of VP structures, pattern of VP closure (coronal, sagittal, or circular), and an underlying occult cleft palate.[3] In patients with neurological deficits or who are poor surgical candidates, evaluation by a prosthodontist for oral prosthetics is recommended.[24]

A cleft palate most commonly causes VPI secondary to anatomic abnormality. Delayed primary cleft palate repair after 18 months is associated with a higher incidence of speech impairment and VPI.[46][47] However, the timing of VPI surgery has not been shown to affect long-term speech outcomes. Pamplona et al showed that earlier surgical treatment of VPI did not affect postoperative speech therapy.[48] Studies have shown that the success of VPI surgery and speech therapy is influenced mainly by the quality of speech therapy as opposed to the timing of the surgery.[49] Thus, older patients should not be denied surgery because they might not benefit due to their age. Neither speech therapy nor surgery alone can resolve the poor articulation from VPI, and patients often require a combination of speech therapy and surgical interventions.[23][49]

Prognosis

Several studies note a successful reduction in hypernasality with pharyngoplasty up to 85%.[50][51] Failure after VPI surgery can present in 4% to 12% of patients who may require additional or revision surgery.[3] Several studies did not find gender, age, palatal defects, prior adenoidectomy, or IQ to be predictors of postoperative speech outcomes.[52][53][54][55][56]

In a systematic review of patients with 22q11 microdeletion syndrome and VPI, there was no significant difference in speech outcome or morbidity between the different types of pharyngeal flaps.[4] Rates of failures from primary pharyngeal flap and sphincter pharyngoplasty have been equal, with both techniques being amenable to salvage through revision surgery.[55]

Complications

Complications from surgical intervention involve obstruction of nasal airflow, hyponasal speech, persistent hypernasal speech, and obstructive sleep apnea (OSA). The pharyngeal flap has been associated with lateral port stenosis, hyponasal voice secondary to over-obturation of the nasopharynx, and postoperative OSA in up to 20% of patients.[3][57] Native mucosa should be used to cover any exposed muscle during flap elevation to prevent tissue contraction and suboptimal obturation of the VP port. An increased risk of postoperative OSA has been found with sphincter pharyngoplasty requiring flap revision.[58]

Risks of posterior pharyngeal wall augmentation include migration or extrusion of injected material, foreign body reaction, and fat embolism.[59] Persistent VP gap and hypernasal speech can be treated with a combined surgical approach using both sphincter pharyngoplasty and Furlow palatoplasty. This combination approach requires significantly less surgical revision than pharyngeal flap or sphincter pharyngoplasty alone.[60]