Figure 183.1.— Lower motor neuron facial weakness. [A] Asymmetrical facial grimacing. [B] Brain CT demonstrating an abnormal left petrous bone.
Facial nerve damage with or without radiological evidence of petrous bone malformation occurs in CHARGE association (Figure 183.2). CHARGE stands for coloboma, heart disease, atresia choanae, retarded growth and retarded development, genital hypolasia, and ear anomalies. In a large series, facial palsy occurred in 38% of patients with CHARGE association.
Figure 183.2.— CHARGE association. [A] Asymmetrical facial grimacing and cleft palate. [B] Ear abnormality.
nerve damage due to parotid gland tumor
Figure 183.3— Facial asymmetry due to parotid gland hemangioma. The asymmetry is present [A] while crying but [B] not during quiet awake. [C] The parotid hemangioma creates a bluish mass behind the ear.
Diagnosis of facial nerve lesion
of the etiology, the diagnosis of a facial nerve lesion may be confirmed
by electrodiagnostic studies. Nerve conduction studies determine threshhold,
latency, and amplitude of the compound muscle potential in the normal
and the affected side. Electromyography shows fibrillations and positive
sharp waves 12 to 14 days after the injury. An EMG abnormality in the
first 48 hours of life implies that the injury occurred before delivery.
Computed tomography of the petrous bone may be used to evaluate the osseous
facial nerve canal and the middle ear.