paralysis of the diaphragm

Diaphragmatic paralysis usually results from the interruption of nerve impulse transmission through the phrenic nerve. It may be unilateral or bilateral. The most common cause is the phrenic nerve invasion by a neoplasm, usually of pulmonary origin, although many cases are idiopathic. In these idiopathic cases, the paralysis is almost invariably right-sided and usually occurs in males. Traumatic injury of phrenic nerve can occur after radical neck or cardiothoracic surgery (stretch, section, or hypothermia), cervical manipulation, and cervial venipuncture. Patients with unilateral diaphragmatic paralysis are usually asymptomatic, although some patients may complain of dyspnea on effort. A paralyzed hemidiaphragm shows an elevated and accentuated dome configuration in both posteroanterior and lateral projection of chest radiographs (Fig 1). If the paralysis is left-sided, the stomach and splenic flexure of the colon relate to the inferior surface of the elevated hemidiaphragm and usually contain more gas than normal. The sniff test on fluoroscopy is considered the most reliable way to detect diaphragmatic paralysis. The sniff test is accomplished by having the patient inhales rapidly and forcefully through the nose with the mouse closed. Normally both hemidiaphragms descend sharply during a sniff (Fig 2). Paradoxical upward motion of an entire hemidiaphragm, as seen in oblique or lateral projection, of greater than 2 cm is considered to diaphragmatic paralysis. Recruitment of abdominal expiratory muscles can cause a false-negative test. Definitive diagnosis of phrenic nerve paralysis can be obtained by cervical phrenic nerve stimulation with electromyographic measurement.

Fig 1: PARALYSIS OF THE DIAPHRAGM DUE TO TRAUMATIC INJURY OF PHRENIC NERVE (CONTUSION OF SCALENUS ANTERIOR)

Suspicion of diaphragmatic rupture in a 45-year-old man with motor vehicle accident 2 days earlier. Fig 1a. Chest radiograph: elevation of right hemidiaphragm and segmental atelectasis in the lower lobe. CT scan of the thorax shows no abnormality of the right diaphragm.

Fig 1b. CT section at the lower cervical level: multiple ill-defined low-density area in the enlarged right scalnus anterior (arrow), medius, and posterior muscles corresponding to contusion.

Fig 2. NORMAL DIAPHRAGMATIC MOVEMENT DURING A SNIFF. Video shows a sharp descent of the diaphragm during a rapid inspiration in a 50-year-old healthy woman.