Dysgeusia and paresthesia following suspension microlaryngoscopy: review and recommendations for risk reduction

Abstract

Background

Dysgeusia or altered taste is a rare complication following suspension microlaryngoscopy with the incidence ranging from 2.9 to 12.1%. We report this with recommendations to avoid similar complications following suspension laryngoscopy, tonsillectomy, and tongue base surgery which require pressure to be placed on the tongue for better surgical field visualization.

Case presentation

A 53-year-old man with underlying diabetes mellitus presented with long standing history of irritative cough, globus sensation, and evidence of laryngopharyngeal reflux. A left ventricle swelling was noted on flexible laryngoscopy and neck. He underwent direct laryngoscopy and biopsy of the left ventricle lesion which revealed to be acute on chronic inflammation. Day 1 postoperatively, patient complained of reduced sensation over left hemi-tongue. A referral to a neurologist was made for further examination and he was found to have loss of taste over anterior two-third of tongue and treated with vitamin B complex. To date, dysgeusia remains persistent. Patient relayed his grievances to the hospital following these complications. Review of literature on relevant topic was made through PubMed, Web of Science, and Cochrane Library Database by two reviewers, working independently. Twenty-three papers, available in full, written in English language, containing number of cases, type of surgery, and complications were extracted and studied.

Conclusions

Risk of dysgeusia and paresthesia postoperatively should be informed during consent taking for all patients undergoing tonsillectomy, laryngeal microsurgery, and tongue base surgery. Zinc deficiency should be investigated in patients with persistent taste disturbance post-tonsillectomy. Intermittent release during suspension laryngoscopy beyond 30 min to reduce post-surgical complications. Greater care should be taken to reduce the amount of force during the suspension laryngoscopy due to smaller oral and oropharyngeal structure in female. Keeping close to the tonsillar capsule particularly in mid and lower pole areas should be done in tonsillectomy using diathermy dissection.

Background

Dysgeusia and paresthesia are complications of suspension laryngoscopy with the incidence range of 2.9–12.1% and 5.7–18% respectively. Although it is a benign complication and not life threatening, it may be life altering and lead to litigation if the risks of surgery are not properly explained to the patient. Dysgeusia and paresthesia were also reported in other surgeries such as tongue base reduction or tonsillectomy when pressure is placed on the tongue for better surgical field visualization. Following a medicolegal case revolving dysgeusia and paresthesia after suspension laryngoscopy in our center, we discuss the case, review past literature, and extracted recommendations to reduce the risk of these complications. This paper also intends to create awareness on the complications and ensure that the risks are explained to the patient prior to surgery to avoid potential medicolegal issues.

Case presentation

A 53-year-old man with underlying type 2 diabetes mellitus, hypertension, and dyslipidemia presented to our Otorhinolaryngology clinic complaining of long standing irritative cough since the year 2000. He also had symptoms of globus sensation, acid brash, and halitosis. There was no hoarseness, dysphagia, altered taste, or constitutional symptoms. Patient was a nonsmoker. Flexible nasopharyngolaryngoscopy showed granular posterior pharyngeal wall and presence of a small smooth left ventricle swelling. Vocal fold mobility was normal. Neck computer tomography scan showed asymmetry of the ventricles with fullness on the left side anteriorly, adjacent to the left thyroid cartilage.

The patient was treated for laryngopharyngeal reflux and subsequently underwent a direct laryngoscopy and biopsy of the left ventricle lesion. Patient was obese class I; however, there was no difficulty during the intubation. He was intubated with a microlaryngeal tube size 6 and HAVAS laryngoscope with suspension was used for the procedure (Fig. 1). The procedure lasted for 2 h with no intermittent release of pressure in between. Mass at the anterior third of left ventricle was completely excised and histopathology revealed to be acute on chronic inflammation with no malignancy.

Fig. 1

Suspension laryngoscopy set used in our center, pictured are HAVAS laryngoscope

He complained of reduced sensation over left hemi-tongue at day 1 post-operation. He was conservatively treated with vitamin B complex. Due to persistent complaints despite medication, a referral to the Neuromedical team was made at 5 months post-operation. Monadic taste testing was done and was found to have loss of taste over anterior two-third of tongue. Taste sensation of the posterior third of the tongue was intact. He was advised for stimulation of taste bud with sugar, salt, and coffee. To date, his dysgeusia remains persistent. Patient expressed his grievance on the unfortunate complication.

Review of literature

The search terms used were “dysgeusia,” “parageusia,” “taste disturbance,” “taste distortion,” “taste change,” “metallic taste,” “altered taste,” “paresthesia,” “laryngoscopy,” “laryngeal microsurgery,” “tonsillectomy,” and “tongue surgery” for advanced search in titles and abstracts in PubMed, Web of Science, and Cochrane Library Database. Two reviewers, working independently, scanned the abstracts and titles for relevance. Only full papers written in English were included in our review. Review articles and letters to editors were excluded.

From 1668 papers published up to August 2023, 38 were identified as relevant based on their title and abstract. Data from 23 of these papers, which were available in full text, written in English, and contained information on the number of cases and complications from suspension laryngoscopy (Table 1), tonsillectomy (Table 2), and tongue base surgery (Table 3), were extracted and studied. Review articles and letters to editors were excluded. Recommendations were made based on literature review.

Table 1 Review of literature for dysgeusia and paresthesia after suspension laryngoscopy

Table 2 Review of literature for dysgeusia and paresthesia after tonsillectomy

Table 3 Review of literature for dysgeusia and paresthesia after tongue base surgery

Discussion

Taste is described as the perception that originates in the taste buds and is transmitted via the chorda tympani to reach the facial nerve, the glossopharyngeal nerve (GN), and the upper laryngeal branch of the vagus nerve. There are four fundamental taste sensations that can be identified: sweet, salty, sour, and bitter. [13] Dysgeusia (taste disturbance) and tongue paresthesia (paresthesia) following tonsillectomy, suspension laryngeal surgery, and tongue base surgery is uncommon. However, dysgeusia has been listed in ICD-11 and carries significant morbidity [2].

Tongue symptoms pre and postoperatively can be assessed by questionnaires, chemical gustatory test, or electrogustometry method. Chemical gustometry is a technique used to explore the various regions of tongue innervation. [13] Chemicals that may be used for taste are as follows: sweet, 0.4 g/mL sucrose; sour, 0.075 g/mL citric acid; salty, 0.25 g/mL sodium chloride; and bitter, 0.0015 g/mL quinine-hydrochloride. [22] In electrogustometry, a nodal stimulation with a continuous current is given until a metallic sensation is detected in different zones of buccal cavity to direct the location of nerve damage [13].

Lindemann et al. reported 6 out 63 patients who underwent suspension laryngoscopy had tongue complaints such as swelling, numbness, taste disturbance, and temporary difficulty with voluntary tongue movement. [8] The mean duration of suspension for patients who reported postoperative tongue symptoms was 37.8 min, with a range of 11 to 60 min. In contrast, for patients without postoperative tongue symptoms, the mean suspension time was shorter: 30.9 min, ranging from 2 to 71 min. Tessema et al. reported surgical time of 30 to 60 min causes increased risk of developing tongue-related symptoms nearly 3 times. Surgical time of over 1 h increased risk to 5 times. [2] In our case, the tongue suspension during direct laryngoscopy was about 2 h without release of pressure in between which may carry higher risk in developing tongue-related symptoms postoperatively.

Higher suspension force is also predictive of postoperative tongue symptoms. [5, 8] Lindemann et al. reported higher mean force of suspension 6.38 ± 2.08 kg in symptomatic group to be compared to 4.84 ± 2.33 kg in asymptomatic group. [8] Feng and Song reported patients without complication had a mean suspension force of 72.8 Newton (N) whereas patients with complications had a mean force of 126.6 N. The comparison between the two groups were statistically significant (p < 0.01). [5] Illustration of tongue compression during suspension laryngoscopy and tonsillectomy are shown in Figs. 2 and 3 respectively.

Fig. 2

Tongue compression during suspension laryngoscopy

Fig. 3

Tongue compression during tonsillectomy

Post-tonsillectomy, taste recognition in the posterior tongue regions tasting bitter and sour is more affected than anterior tongue regions tasting sweet and salty. [20] This is possibly due to the angulation and placement of the Davies-Boyle retractor blades. For our post-suspension laryngoscopy patient, taste affected is at the region of anterior 2/3 of the tongue. The taste topography of the tongue is illustrated in Fig. 4.

Fig. 4

Distribution of taste on tongue surface

Female patients were reported to be 5.5 times more likely to get tongue-related symptoms than male. [2] The increase incidence in female may be due to smaller oral and oropharyngeal anatomic structure such as smaller jaw, higher larynx, and thinner tongue [5, 6]. Less soft tissue would result in shorter distance to nearby neurovascular structures and thus less cushioning to absorb the pressure exerted by the laryngoscope on the tongue and mandible. Greater care should be taken to reduce the amount of force for female during the suspension laryngoscopy [5].

Possible cause of dysgeusia following tonsillectomy is injury to lingual branch of the glossopharyngeal nerve (LBGN) during the removal of the inferior part of the tonsil, retractor pressure on the tongue, post-surgery zinc deficiency due to lack of food intake, and medication adverse effects. [1, 10, 15] Tomofuji et al. reported the number of patients with silent zinc deficiency increased from 13 (37.1%) before surgery to 20 (57.1%) after surgery and recommended consideration of zinc deficiency in patients with taste disturbance due to reduced post-tonsillectomy food intake. [1] Tomita and Ohtuka reported that 2 out of 11 cases of taste disturbance post-tonsillectomy were diagnosed being due to medications. In one patient, it was suspected due to labetalol and medazepam. [10] Taste recovered after 6 months with zinc sulfate supplement despite same dose of labetalol.

Smithard et al. reported that patients who underwent tonsillectomy with bipolar dissection were more likely to suffer altered taste than those who had cold steel dissection (p < 0.019). [14] Extensive dissection of the tonsillar bed, especially in cases where the lingual branch of the glossopharyngeal nerve adheres to the tonsillar capsule, carries a higher risk of nerve damage. When using bipolar dissection methods, more thermal damage occurs beyond the tonsillar capsule compared to “cold steel” techniques. This increased thermal damage could account for the notably higher occurrence of nerve damage reported with the use of bipolar dissection. [14] They suggested keeping close to the tonsillar capsule particularly in mid and lower pole areas when diathermy dissection is used.

Dysgeusia after tongue base resection or radiofrequency reduction for OSA patients may be due to direct injury to taste buds, taste sensory nerve branch damage, excessive excision of taste receptors on the tongue base, wound healing post-inflammatory process, or mechanical pressure to the tongue base by the suspension suture. [22, 23]

Identification of risk factors of tongue complications for these surgeries is imperative to prevent complications. Patients should be thoroughly explained regarding complication risks while consent is obtained to avoid anxiety and medicolegal pursuit. From our review, we note that conservative therapy comprising of medical treatment such as combination of vitamins B1, B2, B8, B12, and steroid as well as zinc sulfate therapy for those with zinc deficiency is prescribed. Patients have variable recovery period. Most patients recovered between 1 week and 6 months; however, there are cases which persisted beyond 1 year.

Conclusion and recommendation

• 1. Risk of dysgeusia and paresthesia postoperatively should be informed during consent taking for all patients undergoing tonsillectomy, laryngeal microsurgery, and tongue base surgery.

• 2. Zinc deficiency should be investigated in patients with persistent taste disturbance post-tonsillectomy.

• 3. Intermittent release during suspension laryngoscopy beyond 30 min to reduce post-surgical complications.

• 4. In female, greater care should be taken to reduce the amount of force during the suspension laryngoscopy due to smaller oral and oropharyngeal structure.

• 5. Keeping close to the tonsillar capsule particularly in mid and lower pole areas in diathermy dissection tonsillectomy.