tears), in which fibers originally supplying mandibular and sublingual glands reinnervate the lacrimal gland by way of the greater superficial petrosal nerve. This syndrome usually develops after severe injury to the proximal seventh nerve and may be accompanied by decreased reflex tearing and decreased taste from the anterior two-thirds of the tongue.

Seventh Nerve Disorders

Disorders of Underactivity of the Seventh Nerve

Facial weakness or paralysis may occur with supranuclear, nuclear, or infranuclear lesions (Table 11- 3).

Table 11-3

Supranuclear lesions

A frontal lesion in the facial portion of the precentral gyrus results in a contralateral paralysis of volitional facial movement, which involves the lower face more severely than the upper face (upper motor neuron lesion). Emotional and reflex facial movements such as smiling and spontaneous blinking are usually preserved because they are controlled through extrapyramidal pathways.

With extrapyramidal disorders, such as parkinsonism or progressive supranuclear palsy, spontaneous facial expression is minimal, and the spontaneous blink rate is usually reduced. Volitional facial movements generally remain intact.

Brainstem lesions

Ipsilateral facial weakness involving both the upper and lower face may occur with a pontine disorder. Vascular lesions and intraparenchymal tumors are the most common causes. Other evidence of a pontine disturbance is to be expected, such as ipsilateral corneal and facial anesthesia, sixth nerve palsy, lateral gaze palsy, cerebellar ataxia, and contralateral hemiparesis. Dissociations between the autonomic, sensory, and motor functions of the seventh nerve may be present. Large lesions of the pons may produce facial diplegia, which also occurs in Möbius syndrome, a congenital disorder involving bilateral sixth nerve palsies.

Peripheral lesions

Peripheral or lower motor neuron lesions result in ipsilateral facial weakness and may have numerous causes. Testing sensory and autonomic functions of the seventh nerve helps pinpoint the responsible lesion. Concomitant impairment of the fifth, sixth, or eighth cranial nerves or cerebellar signs may indicate cerebellar pontine angle tumors.

Bell palsy, which typically occurs in adults, represents the most common type of facial neuropathy, but it must remain a diagnosis of exclusion. Bell palsy is characterized by the sudden onset of facial paresis. Pain may either precede the palsy or occur concurrently. Facial numbness may be reported, although cutaneous sensation is usually intact. Decreased tearing, diminished taste, and dysacusis also may be noted.

Although the etiology of Bell palsy is unknown, the palsy may be caused by autoimmune or viralinduced inflammatory or ischemic injury with swelling of the peripheral nerve. The incidence of Bell palsy is higher in pregnant women and in patients with diabetes mellitus or a family history of Bell palsy. If the facial weakness progresses over a period of more than 3 weeks, an alternative etiology should be considered (eg, a neoplastic process or an inflammatory disorder such as sarcoidosis).

Approximately 85% of patients with Bell palsy experience a satisfactory spontaneous recovery, although subtle signs of aberrant regeneration are commonly present. In these patients, recovery typically begins within 3 weeks of onset of the deficit and is complete by 2–3 months. In the remaining patients, recovery is incomplete, and aberrant regeneration is common. Complete facial palsy at the time of presentation, impairment of lacrimation, dysacusis, and advanced age are all poor prognostic signs. Electrical stimulation testing provides an assessment of the degree of nerve degeneration and has been reported to be helpful in predicting recovery.

Corticosteroids are commonly used to treat Bell palsy, and evidence from meta-analyses and randomized trials supports their efficacy. It is postulated that edema of the nerve within a tight fallopian canal contributes to nerve damage, and a 7–10-day course of oral corticosteroids is recommended for patients without specific systemic contraindications who are evaluated within the first 72 hours. Several experimental and clinical reports have suggested that a combination of antiviral agents (eg, acyclovir, famciclovir, valacyclovir) with corticosteroids may provide additional benefit over the use of corticosteroids alone in the treatment of Bell palsy. However, several other large trials found that, although corticosteroids improved the chances of recovery, the use of an antiviral drug, either alone or in combination with corticosteroids, conferred no benefit.

Neoplasms may involve the seventh nerve in the cerebellopontine angle (eg, acoustic neuroma [Fig 11-9], meningioma), within the fallopian canal, or in the parotid gland. Such lesions can compress the seventh nerve, resulting in facial synkinesis. Most of these lesions are histologically benign and slow growing and best evaluated through magnetic resonance imaging (MRI) with intravenous contrast.

Figure 11-9 Facial nerve palsy. This 60-year-old patient experienced ocular irritation on the left side after excision of a left acoustic neuroma. A, The left eye will not close due to weakness of the left orbicularis oculi. B, Fortunately, corneal sensation remains intact, and the patient demonstrates an excellent Bell phenomenon. (Photographs courtesy of Steven A.

Newman, MD.)

Various infectious agents can cause seventh nerve pathology. The nerve may be impaired from meningitis. Lyme disease, caused by infection with the tick-borne spirochete Borrelia burgdorferi, can cause unilateral or bilateral facial palsies. Classic manifestations include a characteristic rash, arthritis, and meningopolyneuritis (see Chapter 14). The prognosis for seventh nerve recovery following treatment of Lyme disease is excellent.

Herpes zoster involving the seventh nerve is called Ramsay Hunt syndrome. It is diagnosed through the identification of vesicles along the posterior aspect of the external auditory canal, over the tympanic membrane, or on the pinna. Pain is often severe, and postherpetic neuralgia may result. The prognosis for recovery is less promising than for Bell palsy. An isolated seventh nerve palsy, as well as other isolated or multiple cranial nerve palsies, may be the first sign of human immunodeficiency virus (HIV) seroconversion. Infectious disorders such as otitis media may spread to involve the seventh nerve.

The seventh nerve is the cranial nerve most commonly involved in sarcoidosis. The site of involvement is usually the parotid gland, which develops noncaseating granulomatous inflammation. Seventh nerve involvement is frequently bilateral yet asymmetric.

Facial diplegia may occur in Guillain-Barré syndrome, especially in the variant Miller Fisher syndrome, when ophthalmoplegia and ataxia are also present. Cerebrospinal fluid analysis reveals an elevated protein level with a normal cell count, and deep tendon reflexes are usually absent. A high percentage of patients with Miller Fisher syndrome have anti-GQ1b IgG antibodies in their serum. Recovery is generally complete, and the serologic test results improve with clinical improvement.

A seventh nerve palsy may occur with head trauma. The Battle sign (ecchymosis over the mastoid area) may be present and is associated with fractures of the temporal bone. Congenital facial palsy is frequently related to birth trauma from use of forceps and tends to resolve.

In Melkersson-Rosenthal syndrome, recurrent unilateral or bilateral facial paralysis is accompanied by chronic facial swelling and lingua plicata (furrowing of the tongue). The etiology of this disorder, which usually begins in childhood or adolescence, is unknown. The facial swelling is frequently marked and may be bilateral, even when facial paresis is only unilateral.

Given the extensive differential diagnosis for seventh nerve weakness, etiologic considerations in

Essential blepharospasm

This bilateral condition consists of episodic contraction of the orbicularis oculi. Onset usually occurs between ages 40 and 60 years. Initially, the spasms are mild and infrequent, but they may progress to the point that the patient’s daily activities are severely disrupted. In advanced cases, the patient’s eyelids cannot be pried open during an episode of spasm. Facial grimacing and other movements may be associated with blepharospasm (Meige syndrome) (Fig 11-10), and cogwheeling in the neck and extremities or other extrapyramidal signs may be noted. Tardive dyskinesia secondary to neuroleptic and antipsychotic drugs can produce spasms that involve the mouth. Extrapyramidal disorders such as parkinsonism, Huntington disease, and basal ganglia infarction may be accompanied by some degree of blepharospasm.

Figure 11-10 Essential blepharospasm with Meige syndrome. This patient has contraction of the orbicularis oculi muscles in association with facial grimacing. (Courtesy of Eric Eggenb erger, DO.)

The exact cause of benign essential blepharospasm is unknown, but increasing evidence using functional neuroimaging suggests that it is caused by basal ganglia dysfunction. The clinician evaluating a patient with blepharospasm should exclude causes of reflex blepharospasm, in particular severely dry eyes, intraocular inflammation, and meningeal irritation (usually associated with photophobia). Stress may exacerbate the condition. Neuroradiologic studies are generally unrevealing and rarely indicated.

The efficacy of medical therapy for blepharospasm, including use of neuroleptics and benzodiazepines, is generally limited. Tinted lenses such as FL-41 tint may improve blink frequency and light sensitivity. The treatment of choice for essential blepharospasm is injection of botulinum

toxin type A (onabotulinumtoxinA, incobotulinumtoxinA, or abobotulinumtoxinA) into the orbicularis oculi muscle. The effect of the toxin is temporary, lasting only a few months, so that repeat injections are necessary. The efficacy of the drug relates to its ability to cause muscle weakness. Complications such as ptosis, local ecchymosis, ectropion, diplopia, lagophthalmos, and exposure keratopathy are usually mild and transient. Treatment typically consists of 4–8 injection sites per eye. The central portion of the pretarsal orbicularis oculi muscle should be avoided to minimize the chance of inducing ptosis. For patients in whom type A botulinums fail, botulinum toxin type B (rimabotulinumtoxinB) may be an alternative.

Occasionally, when medical treatment fails, surgical therapy consisting of the meticulous extirpation of the eyelid protractors may be indicated. Selective ablation of the seventh nerve is an alternative procedure that carries the risk of greater complications and has a lower success rate. See also BCSC Section 7, Orbit, Eyelids, and Lacrimal System.

Essential blepharospasm may cause psychological distress, with some patients withdrawing socially as the symptoms worsen. Thus, counseling may be as valuable as the medical and surgical management of the condition. The Benign Essential Blepharospasm Research Foundation (BEBRF) (h ttp://www.blepharospasm.org) aids research efforts and provides education and support to blepharospasm patients.

Dutton JJ, Fowler AM. Botulinum toxin in ophthalmology. Surv Ophthalmol. 2007;52(1):13–31.

Hallett M, Evinger C, Jankovic J, Stacy M; BEBRF International Workshop. Update on blepharospasm: report from the BEBRF International Workshop. Neurology. 2008;71(16):1275–1282.

Hemifacial spasm

Hemifacial spasm is characterized by unilateral episodic spasm that involves the facial musculature and typically lasts from a few seconds to minutes. The disorder frequently begins as intermittent twitching of the orbicularis oculi muscle but, over the course of several years, spreads to involve all the facial muscles on 1 side (Fig 11-11). Episodes may increase in frequency for weeks to months and then abate for months at a time. Seventh nerve function is usually intact, although over time subtle ipsilateral facial weakness may develop.

Figure 11-11 Hemifacial spasm. This 73-year-old woman has intermittent twitching involving the entire right side of the

face. (Courtesy of Rod Foroozan, MD.)

The pathogenesis of hemifacial spasm is most commonly compression of the seventh nerve root exit zone by an aberrant vessel. Abnormal firing in the motor nucleus or ephaptic transmission of nerve impulses causes innervation directed toward one muscle group to excite adjacent nerve fibers directed to another muscle group. Less commonly (perhaps 1% of hemifacial spasm), tumors within the cerebellopontine angle or previous injury to CN VII may lead to the spasms; therefore, MRI of the brain, including the course of the facial nerve, is typically performed to exclude a compressive lesion.

Botulinum toxin type A injection into the periocular and facial muscles has proved very effective and is the treatment of choice for hemifacial spasm in most patients. Reinjection is required, with typical intervals of 3–4 months. Hemifacial spasm responds to lower doses of botulinum toxin than does blepharospasm. Adverse effects are similar to those for patients with blepharospasm treated with botulinum toxin.

Carbamazepine, clonazepam, or baclofen may provide improvement in some patients. Suboccipital craniectomy with placement of a sponge between the seventh nerve and the offending blood vessel (microvascular decompression) may be considered for advanced cases or younger