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MEDICAL INTELLIGENCE

CURRENT CONCEPTS

Sialorrhea*

RICHARD ALAN SMITH, M.D., AND
RICHARD L. GOODE, M.D.

During infancy drooling is accepted as a normal part of development. After this period salivary incontinence is culturally unacceptable. For the child with cerebral palsy drooling not only is a social burden but also may further handicap his already difficult task of acquiring speech. Within the last few years new methods to control sialorrhea have been developed. It is our intention to discuss the problem of drooling and to review the advantages and limitations of available therapies. Although this discussion is primarily concerned with the management of drooling, it has implications for the therapy of salivary-duct fistula, tracheoesophageal fistula and chronic sialadenitis.

PROBLEM
Some reports have stressed the role of hypersalivation in the genesis of drooling, but in most cases we believe that drooling results from failure to swallow salivary secretions or from inability to retain the accumulated secretions within the mouth because of a seventh-nerve palsy or facial disfigurement. Hypersalivation may be associated with many disorders such as herpetic stomatitis, irritation by dentures and pregnancy, but drooling does not occur in these cases unless the ability to hold secretions within the mouth or the ability to swallow secretions is impaired. Patients with hypersalivation may expectorate repeatedly, but this is not drooling. It is the difference between salivary production and the ability to swallow saliva that results in drooling rather than the absolute production of saliva.

Difficulty in swallowing saliva is encountered at three levels of function: the oral, pharyngeal and esophageal components of deglutition. Some of the common disorders associated with drooling, classified according to the presumable level of malfunction, are as follows: oral (cerebral palsy, Parkinson's disease, motor-neuron disease, seventh-nerve palsy, facial disfigurement and radical cancer surgery); pharyngeal (motor-neuron disease, myasthenia gravis and polymyositis); and esophageal (carcinoma or stricture).

BACKGROUND
The majority of oral secretions are contributed by the submandibular and parotid glands, which equally provide 80 to 90 per cent of the saliva. The remainder is formed by sublingual and minor salivary glands. One thousand to 1500 ml of saliva is produced daily. Saliva contributes to the digestion of food and to the maintenance of oral hygiene. Without normal salivary function the frequency of dental caries increases significantly.

Both the sympathetic and the parasympathetic nervous systems innervate the salivary glands. It is evident that the sympathetic nervous system, although its role in salivation is still controversial, influences the blood flow to the salivary glands and activates myoepithelial cells within the salivary ducts. These myoepithelial cells expedite the flow of saliva by squeezing saliva out of the salivary glands. The major neural pathways are shown in Figure 1.

Most methods to control salivary secretion attempt to alter the functional competence of the salivary glands. In general all four major glands must be treated because unaltered glands may compensate for the decrease of saliva production.

THERAPY

Drugs
The parasympathetic nervous supply to the salivary glands is mediated by cholinergic terminals. Therefore, antisialogogues are primarily anticholinergic drugs, such as atropine and scopolamine, or drugs that have anticholinergic properties (phenothiazines and ganglionic-blocking agents) in addition to other effects.

Most clinical studies of antisialogogues have assessed the usefulness of these agents in the practice of anesthesia. These studies suggest the following results of acute administration of antisialogogues: similar antisialogogic effect can be achieved by most anticholinergic drugs with modification of their dose; oral administration of anticholinergic drugs in clinically acceptable doses reduces salivary output but does not arrest salivation; individual variations to the therapeutic response of antisialogogues are common; and selection of an antisialogogue will be dictated more by the nature of the side effects than by a special ability of any agent to limit salivation.

Some of these generalizations might be expected to apply to chronic administration of antisialogogues; however, long-term use of antisialogogues is generally not a successful therapy for drooling. It is reasonable to recommend the use of antisiaogogues in the initial attempts to control sialorrhea, but the patient should be reassured that a variety of other therapies are available if drug therapy proves to be unsatisfactory. In combination with other therapies the presently available drugs may be helpful.

Radiotherapy
There is a justifiable reluctance to consider radiotherapy for the control of salivary secretions. In most cases it seems inappropriate to substitute the dangers of radiation for the inconvenience of drooling. However, when drooling occurs in association with a terminal illness use of radiotherapy may be warranted.

Administration of 400 to 1000 rads of x-ray temporarily reduces the secretary capacity of the salivary glands, but approximately 4000 rads are required to produce permanent atrophy. Individual variation in response to radiotherapy is common. In fact individual salivary glands in one patient may respond differently to radiation.

Surgery
Denervation. The effects of denervation of the salivary glands have been studied extensively. For the purpose of this discussion only the effects of parasympathetic denervation will be mentioned because the parasympathetic nervous system supplies the major, if not all, secretomotor fibers to the salivary glands. After parasympathetic denervation the salivary glands atrophy, and the resting and reflex secretion markedly diminishes.

Two approaches to surgical denervation have been reported. In one approach the submandibular-sublingual glands are denervated by excision of the submandibular ganglions, and the parotid gland is denervated by section of the auriculotemporal nerve. During section of the auriculotemporal nerve the facial nerve may be accidentally injured.

The other surgical approach capitalizes on the fortuitous anatomic relation of the tympanic plexus and the chorda tympani within the middle ear. These nerves carry the parasympathetic innervation to the salivary glands on one side (Fig. 1). In their location within the middle ear both the chorda tympani and the tympanic plexus are readily sectioned with the use of standard otologic technics. Because of the relative ease of this procedure trans-tympanic neurectomy has gained acceptance as the procedure of choice for denervation of the salivary glands. After section of one chorda tympani, unilateral loss of taste on the anterior two thirds of the tongue occurs, but this is a minor inconvenience. After bilateral section of the chorda tympani loss of taste may evoke complaint from the patient. Regeneration of the sectioned nerves may occur and necessitate further therapy.

Salivary-duct ligation. Ligation of the salivary ducts has been advocated since the early 1900's for the treatment of salivary-duct fistula and sialadenitis as well as for the reduction of salivary secretion. Surgical ligation of the salivary ducts is accomplished with relative ease, and the results are immediate. Unfortunately, ligation of the ducts of normal salivary glands is often associated with complications. Postoperative pain and swelling occur, particularly when the patient is eating. This results from dilatation of the salivary ducts and may last for several weeks. The postoperative discomfort may be partially relieved by the use of drugs. Therapeutic salivary-duct ligation may be more acceptable if the postoperative pain and swelling can be moderated by the use of preoperative denervation, radiotherapy or drug administration.

Glandular excision. Excision of the submandibular glands is readily accomplished under local anesthesia. The parotid glands are not easily removed. This mode of controlling salivary secretion from the submandibular glands may be useful when alternate forms of therapy have been unsuccessful.

Salivary-duct translocation. This technic is a potential form of therapy for patients whose drooling results from inability of the tongue to effect successful propulsion of saliva posteriorly into the pharynx. In this procedure the flow of parotid saliva is directed from the parotid ducts to the tonsillar fossae and subsequently swallowed. This procedure does not affect the flow from the submandibular and sublingual salivary glands, and further therapy is required. The operation is complicated and of limited application.

We are indebted to Mrs. Ann Clay, Miss S. E. McMillan, Mrs. Marjorie Knight, Mr. Alan Rendes, Mr. David Popoff and Mr. Theodore Steffens for assistance.