Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_1015_Библиотеки_им_академика_М_И_Перельмана

Functional brain imaging studies also showed that the swallowing cortex is represented bilaterally, but asymmetrically, i.e., it is (in most people) bigger on one side than on the other. The bigger swallowing cortex is called the dominant one. Swallowing domi- nance is independent of the language-dominant side or of handedness (Barrit and Smithard 2009; Hamdy et al. 1999).

2009).

2003).

Owing to the role of the brainstem in swallowing, unilateral lesions of the medullary region—such as in Wallenberg’s syndrome caused by unilateral infarc­tions in the supply area of the posterior inferior cer­ebellar artery (Fig. 1)—affecting both ipsilateral CPGs and the NA and the NST, cause complex swallowing disturbances, including unilateral pha­ryngeal paresis (NA), impaired pharyngeal peristalsis (NA and dmCPG), sensory deficits in the oropha­ryngeal region (sensory trigeminal nucleus and NST), and secondary UES opening deficit due to impaired hyolaryngeal excursion and/or primary UES opening disturbance due to impaired sphincter relaxation (dmCPG) (Prosiegel et al. 2005a). Dysphagia may be the sole symptom in dorsolateral medullary infarctions but is—owing to ipsilateral vagal pare­sis—often associated with hoarseness due to unilate­ral vocal cord paresis. Other symptoms belonging to Wallenberg’s syndrome are rotatory nystagmus,

The motoneurons of the swallowing cortex are called first motoneurons or upper motoneurons (UMNs). When the swallowing cortex itself and/or and its axons, i.e., the corticobulbar fibers, are lesioned bilaterally, there is diminished input to the brainstem. The consequence is severe dysphagia which affects predominantly the volitional oral phase. Owing to impaired cortical input, the mem­brane of the motoneurons in the brainstem lower their electrical threshold with consecutive hyperre­flexia (e.g., enhanced masseter reflex) and muscle stiffness in terms of spasticity. There are no muscle atrophies, since the second motoneurons/lower motoneurons (LMNs) in the brainstem are intact and, therefore, able to supply the corresponding muscles with the transmitter acetylcholine. This syndrome is called pseudobulbar palsy and occurs in UMN diseases (UMNDs); examples are amyo­trophic lateral sclerosis (ALS) due to bilateral degeneration of the UMNs or bilateral subcortical infarctions affecting the corticobulbar tracts. In most cases of pseudobulbar palsy, besides dysphagia also dysarthria and chewing problems occur; pathologi­cal crying or laughing is often associated with pseudobulbar palsy too. Bilateral lesions of the corticobulbar tract in the brainstem (e.g., in bilateral anterior mesencephalic infarctions) may also cause pseudobulbar palsy. Very typical for pseudobulbar palsy is automatic–voluntary dissociation: emotional or reflex responses are intact or enhanced, whereas

2002) and is sometimes called cervical achalasia.

Defective tonicity of the UES between swallows (cervical chalasia) may occur in motonic dystrophy, myasthenia gravis, during ‘‘off’’ periods of Parkinson’s disease, and after radiotherapy of the neck; it is often asymptomatic, but may cause aerophagia, belching, and/or regurgitation of refluxed material (Ekberg and Olsson 1995).

examination and MRI are dealt with in Sect. 3.6.

2001a, b). The Standardized Swallowing Assessment