Etiology of vocal cord paralysis
Central causes (10%):
- Cerebral trauma: Hemorrhage, laceration, thrombosis, embolism.
- Cerebral infections: meningitis, encephalitis or brain abscess.
- Brain tumors.
- Bulbar palsy: affect the nucleus ambiguus of the vagus in the medulla, poliomyelitis and diphtheria
Peripheral causes (90%):
- Congenital: hydrocephalus, Arnold Chiari syndrome.
- Traumatic: Surgical trauma: thyroidectomy, neck dissection, cardiovascular & thoracic surgery, skull base surgery.
- Non-surgical trauma: neck injury, fracture skull base.
- Inflammatory: apical pulmonary abscess, tuberculosis, basal meningitis, peripheral neuritis.
- Neoplastic: bronchogenic carcinoma, thyroid malignancy, nasopharyngeal carcinoma, mediastinal tumors.
- Miscellaneous: idiopathic, myasthenia gravis, sarcoidosis, rheumatoid arthritis.
Position of the vocal cord:
Explanation of vocal cord position:
A. Semon’s law
In progressive RLN injury, abductor paralysis occurs 1st >> v.c in median or paramedian position, then adductor paralysis >> cadaveric position.
B. Adductors are more powerful than abductors so, when RLN is injured, adductors takes upper hand.
C. Wagner – Grossman theory:
In RLN injury >> paramedian position by cricothyroid muscle.
In vagal injury >> cadaveric position.
Clinical picture:
(A) Unilateral Cord Paralysis:
Symptoms:
- Asymptomatic (compensation).
- Hoarseness of voice.
- Mild stridor especially during excretion.
- Mild aspiration (affection of sphincter mechanism).
- Lack of buildup of the intrathoracic pressure.
Signs:
By indirect or flexible laryngoscopy:
a) In RLN injury: median or paramedian position.
b) In vagal injury: cadaveric position.
The paralyzed cord appears bowed (flaccid), at a lower level, with the arytenoids leaning inwards
Full head, neck, and chest examination for cause.
Investigations:
- Radiological: plain x-ray chest &neck, barium swallow, thyroid scan, CT scan & MRI of the brain, neck & chest.
- Hematological: CBC, ESR, FBS & viral study.
- Panendoscopy: Nasopharyngoscopy, bronchoscopy, and oesophagoscopy and laryngoscopy.
Treatment:
a. Treatment of the cause.
b. No treatment, if compensation.
c. Surgical treatment:
- 6-12 months to reach maximum compensation.
- Persistent dysphonia and/or aspiration.
Aim: Medialization of the paralyzed vocal cord by:
- Teflon injection.
- Collagen injection.
- Thyroplasty type I through window in the thyroid cartilage.
(B) Bilateral vocal cord paralysis:
1. Bilateral Abductor Paralysis
Etiology: Injury to both RLN (peripheral).
- Surgical trauma. Thyroidectomy, esophageal surgery.
- Peripheral neuritis.
- Neoplastic: cancer thyroid.
Symptoms:
- Good voice but tires easily.
- Stridor may be severe, increase by exertion & infection.
Signs:
- By indirect or flexible laryngoscopy: Vocal cords are in median or paramedian position.
- Head, neck, chest examination for cause.
Investigations: The same.
Treatment:
If sever stridor >> Tracheostomy.
In established cases:laryngeal widening procedure ,3-6 months later.
(a) Endoscopic arytenoidectomy with posterior cordectomy using MLS or laser.
(b) Woodman’s operation. External operation to fix aryternoid laterally.
(c) Reinnervation procedure.
(d) Tracheostomy with speaking valve.
2. Bilateral adductor paralysis
Presents with aphonia & aspiration (fatal)
Ttt: tracheostomy with speaking valve, laryngeal closure, or total laryngectomy.