Lower Brainstem and Cranial Nerve Dysfunction




This chapter will review disorders causing dysfunction of the VII through XII cranial nerves. Many such disorders also disturb ocular motility and the discussion of these is in Chapter 15 . The basis for chapter assignment is by the most usual initial clinical feature. For example, the discussion of myasthenia gravis is in Chapter 15 because diplopia is a more common initial complaint than dysphagia.


An acute isolated cranial neuropathy, such as facial palsy, is usually a less ominous sign than multiple cranial neuropathies and is likely to have a self-limited course. However, an isolated cranial neuropathy may be the first sign of progressive cranial nerve dysfunction. Therefore, the discussion of conditions causing isolated and multiple cranial neuropathies are together because they may not be separable at onset.


Facial Weakness and Dysphagia


Anatomical Considerations


Facial Movement


The motor nucleus of the facial nerve is a column of cells in the ventrolateral tegmentum of the pons. Nerve fibers leaving the nucleus take a circuitous path in the brainstem before emerging close to the pontomedullary junction. The fibers then enter the internal auditory meatus with the acoustic nerve. Fibers for voluntary and reflexive facial movements separate rostral to the lower pons. After bending forward and downward around the inner ear, the facial nerve traverses the temporal bone in the facial canal and exits the skull at the stylomastoid foramen. Extracranially, the facial nerve passes into the parotid gland where it divides into several branches, which innervate all muscles of facial expression except the levator palpebrae superioris, which is innervated by cranial nerve III.


Sucking and Swallowing


The sucking reflex requires the integrity of the trigeminal, facial, and hypoglossal nerves. Stimulation of the lips produces coordinated movements of the face, jaw, and tongue. The automatic aspect of the reflex disappears after infancy but may return with bilateral dysfunction of the cerebral hemispheres.


Fibers of the trigeminal and glossopharyngeal nerves ending in the nucleus solitarius form the afferent arc of the swallowing reflex. The motor roots of the trigeminal nerve, the glossopharyngeal and vagus fibers from the nucleus ambiguous, and the hypoglossal nerves form the efferent arc. A swallowing center that coordinates the reflex is located in the lower pons and upper medulla. A bolus of food stimulates the pharyngeal wall or back of the tongue, and the combined action of the tongue, palatine arches, soft palate, and pharynx move the food into the esophagus.


Approach to Diagnosis


The causes of facial muscle weakness may be supranuclear palsy (pseudobulbar palsy), intrinsic brainstem disease, or disorders of the motor unit: facial nerve, neuromuscular junction, and facial muscles ( Boxes 17-1 and 17-2 ). The differential diagnosis of dysphagia is similar ( Box 17–3 ), except that isolated dysfunction of the nerves that enable swallowing is very uncommon.



BOX 17-1





  • Aplasia of facial muscles



  • Birth injury



  • Congenital myotonic dystrophy (see Chapter 6 )



  • Congenital bilateral perisylvian syndrome



  • Fiber-type disproportion myopathies (see Chapter 6 )




    • Myasthenic syndromes


      Denotes the most common conditions and the ones with disease modifying treatments




    • Congenital myasthenia (see Chapter 15 )



    • Familial infantile myasthenia (see Chapter 6 )



    • Transitory neonatal myasthenia (see Chapter 6 )




Causes of Congenital Facial Weakness


BOX 17-2





  • A utoimmune and P ostinfectious




    • Bell’s palsy


      Denotes the most common conditions and the ones with disease modifying treatments




    • Idiopathic cranial polyneuropathy



    • Miller Fisher syndrome (see Chapter 10 )



    • Myasthenia gravis (see Chapter 15 )




  • G enetic




    • Juvenile progressive bulbar palsy (Fazio-Londe disease)



    • Muscular disorders



    • Facioscapulohumeral syndrome (see Chapter 7 )



    • Facioscapulohumeral syndrome, infantile form



    • Fiber-type disproportion myopathies (see Chapter 6 )



    • Melkersson syndrome



    • Myotonic dystrophy (see Chapter 7 )



    • Oculopharyngeal dystrophy



    • Myasthenic syndromes



    • Congenital myasthenia (see Chapter 15 )



    • Familial infantile myasthenia (see Chapter 6 )



    • Osteopetrosis (Albers-Schönberg disease)



    • Recurrent facial palsy




  • H ypertension



  • I nfectious





  • M etabolic D isorders




    • Hyperparathyroidism



    • Hypothyroidism




  • M ultiple S clerosis ( see C hapter 10 )



  • S yringobulbia



  • T oxins



  • T rauma




    • Delayed



    • Immediate




  • T umor




    • Glioma of brainstem (see Chapter 15 )



    • Histiocytosis X



    • Leukemia



    • Meningeal carcinoma



    • Neurofibromatosis




Causes of Postnatal Facial Weakness


BOX 17-3





  • A utoimmune /P ostinfectious




    • Dermatomyositis (see Chapter 7 )



    • Guillain-Barré syndrome (see Chapter 7 )



    • Idiopathic cranial polyneuropathy



    • Myasthenia gravis


      Denotes the most common conditions and the ones with disease modifying treatments

      (see Chapter 15 )



    • Transitory neonatal myasthenia gravis (see Chapter 6 )




  • C ongenital or P erinatal




    • Aplasia of brainstem nuclei



    • Cerebral palsy (see Chapter 5 )



    • Chiari malformation (see Chapter 10 )



    • Congenital bilateral perisylvian syndrome



    • Syringobulbia




  • G enetic





  • G lioma of B rainstem



  • I nfectious





  • J uvenile P rogressive B ulbar P alsy



Neurological Causes of Dysphagia


Pseudobulbar Palsy


Because the corticobulbar innervation of most cranial nerves is bilateral, pseudobulbar palsy occurs only when hemispheric disease is bilateral. Many children with pseudobulbar palsy have a progressive degenerative disorder of gray or white matter. The discussion of most of these disorders is in Chapter 5 because dementia is usually the initial feature. Bilateral strokes, simultaneous or in sequence, cause pseudobulbar palsy in children; the usual causes are coagulation defects, leukemia, and trauma (see Chapter 11 ). Pseudobulbar palsy is the main feature of the congenital bilateral perisylvian syndrome, discussed in this chapter. Episodic pseudobulbar palsy (oral apraxia, dysarthria, and drooling) may indicate the acquired epileptiform opercular syndrome (see Chapter 1 ).


The characteristic feature of pseudobulbar palsy is an inability to use bulbar muscles in voluntary effort, while reflex movements, initiated at a brainstem level, are normal. Extraocular motility is unaffected. The child can suck, chew, and swallow but cannot coordinate these reflexes for eating; movement of a food bolus from the front of the mouth to the back has a volitional component. Emotionally derived facial expression occurs, but voluntary facial movements do not. Severe dysarthria is often present. Affected muscles do not show atrophy or fasciculations. The gag reflex and jaw jerk are usually exaggerated, and emotional volatility is often an associated feature.


Newborns with familial dysautonomia have difficulty feeding, despite normal sucking and swallowing, because they fail to coordinate the two reflexes (see Chapter 6 ). Box 6-7 summarizes the differential diagnosis of feeding difficulty in an alert newborn. Children with cerebral palsy often have a similar disturbance in the coordination of chewing and swallowing that impairs feeding.


Motor Unit Disorders


Disorders of the facial nuclei and nerves always cause ipsilateral facial weakness and atrophy, but associated features vary with the site of abnormality:



  • 1.

    Motor nucleus: Hyperacusis is present, but taste, lacrimation, and salivation are normal.


  • 2.

    Facial nerve between the pons and the internal auditory meatus: Taste sensation is spared, but lacrimation and salivation are impaired and hyperacusis is present.


  • 3.

    Geniculate ganglion: Taste, lacrimation, and salivation are impaired, and hyperacusis is present.


  • 4.

    Facial nerve from the geniculate ganglion to the stapedius nerve: Taste and salivation are impaired and hyperacusis is present, but lacrimation is normal.


  • 5.

    Facial nerve from the stapedius nerve to the chorda tympani: Taste and salivation are impaired, hyperacusis is not present, and lacrimation is normal.


  • 6.

    Facial nerve below the exit of the chorda tympani nerve: Only facial weakness is present.



Disturbances of cranial nerve nuclei seldom occur in isolation; they are often associated with other features of brainstem dysfunction (bulbar palsy). Usually some combination of dysarthria, dysphagia, and diplopia is present. Examination may show strabismus, facial diplegia, loss of the gag reflex, atrophy of bulbar muscles, and fasciculations of the tongue.


The facial weakness associated with myasthenia gravis and facial myopathies is usually bilateral. In contrast, brainstem disorders usually begin on one side and eventually progress to bilateral impairment. Facial nerve palsies are usually unilateral. The differential diagnosis of recurrent facial palsy or dysphagia is limited to disorders of the facial nerve and neuromuscular junction ( Box 17-4 ).



BOX 17-4





  • F amilial




    • Isolated facial palsy



    • Melkersson syndrome




  • H ypertensive F acial P alsy


    Denotes the most common conditions and the ones with disease modifying treatments




  • M yasthenia G ravis



  • S poradic M ultiple C ranial N europathies



  • T oxins



Causes of Recurrent Cranial Neuropathies/Palsies


Congenital Syndromes


Congenital Bilateral Perisylvian Syndrome


This syndrome results from a disturbance in neuronal migration that results in pachygyria of the sylvian and rolandic regions. Most cases are sporadic. The transmission of familial cases is by X-linked inheritance; such cases are more severe in males than in females ( ).


Clinical F eatures


All affected children have a pseudobulbar palsy that causes failure of speech development (apraxia) and dysphagia. Cognitive impairment and seizures are present in approximately 85 % of cases. The cognitive deficit varies from mild to severe, and the seizures, which begin between 4 and 12 years, may be atypical absence, atonic/tonic, partial, or generalized tonic-clonic.


Diagnosis


Magnetic resonance imaging (MRI) shows bilateral perisylvian gyral dysgenesis including pachygyria, and polymicrogyria ( Figure 17-1 ). Postmortem studies have confirmed the MRI impression.




FIGURE 17-1


MRI of congenital bilateral perisylvian syndrome. This child has lissencephaly and schizencephaly. Bilateral disturbances in the perisylvian region caused a pseudobulbar palsy.


Management


The seizures are usually difficult to control, and corpus callosotomy has been useful in some cases with intractable drop attacks. Speech therapy does not overcome the speech disorder, and instruction in sign language is the better alternative for children of near-normal intelligence. Drooling is very disruptive and may benefit from the use of glycopyrolate, excision of the submandibular glands, ligation of parotid gland ducts, or botulinum toxin injections to the parotid glands.


Congenital Dysphagia


Congenital dysphagia is usually associated with infantile hypotonia and therefore discussed in Chapter 6 . Because the neuroanatomical substrates of swallowing and breathing are contiguous, congenital dysphagia and dyspnea are often concurrent. Isolated aplasia of the cranial nerve nuclei subserving swallowing is not established.


Congenital Facial Asymmetry


The cause of most facial asymmetries at birth is congenital aplasia of muscle and not trauma to the facial nerve. Facial diplegia, whether complete or incomplete, suggests the Möbius syndrome or other congenital muscle aplasia. Complete unilateral palsies are likely to be traumatic in origin, whereas partial unilateral palsies may be either traumatic or aplastic. The term neonatal facial asymmetry is probably more accurate than facial nerve palsy to denote partial or complete unilateral facial weakness in the newborn and emphasizes the difficulty in differentiating traumatic nerve palsies from congenital aplasias. A common cause of asymmetry of the lower face/mouth is the unilateral absence of the depressor anguli oris.


Aplasia of Facial Muscles


Clinical Features


The Möbius syndrome is the best-known congenital aplasia of facial nerve nuclei and facial muscles. The site of pathology is usually the facial nerve nuclei and their internuclear connections. Facial diplegia may occur alone, with bilateral abducens palsies, or with involvement of several cranial nerves ( ). Congenital malformations elsewhere in the body (dextrocardia, talipes equinovarus, absent pectoral muscle, and limb deformities) are sometimes associated features. Most cases are sporadic, but familial recurrence occurs. Autosomal dominant, autosomal recessive, and X-linked recessive modes of inheritance are proposed. Identified loci are on chromosomes 13, 3, and 10.


Other developmental causes of unilateral facial palsy are Goldenhar syndrome , the Poland anomaly , DiGeorge syndrome , osteopetrosis, and trisomy 13 and 18.


Diagnosis


Congenital facial diplegia is by definition a Möbius syndrome. All such cases require MRI of the brain to determine if other cerebral malformations are present. Causes other than primary malformations include intrauterine toxins (e.g., thalidomide), vascular malformations, or infarction.


Electromyography (EMG) can help determine the timing of injury. Denervation potentials are only present if injury to the facial nuclei or nerve occurred 2 to 6 weeks before the study. Facial muscles that are aplastic, as in the Möbius syndrome, or nerve injury occurring early in gestation, do not show active denervation.


Management


Surgical procedures may provide partial facial movement.


Depressor Anguli Oris Muscle Aplasia


Clinical Features


Isolated unilateral weakness of the depressor anguli oris muscle (DAOM) is the most common cause of facial asymmetry at birth. One corner of the mouth fails to move downward when the child cries. All other facial movements are symmetrical. The lower lip on the paralyzed side feels thinner to palpation, even at birth, suggesting antepartum hypoplasia.


Diagnosis


Traumatic lesions of the facial nerve would not selectively injure nerve fibers to the DAOM and spare all other facial muscles. Electrodiagnostic studies aid in differentiating aplasia of the DAOM from traumatic injury. In aplasia, the conduction velocity and latency of the facial nerve are normal. Fibrillations are not present at the site of the DAOM. Instead, motor unit potentials are absent or decreased in number. The pulling of the mouth in the direction of the healthy DAOM when crying often causes the referring physician to believe that this is the abnormal side.


Management


No treatment is available or needed. The DAOM is not a significant component of facial expression in older children and adults, and absence of the muscle is difficult to notice.


Birth Injury


Perinatal traumatic facial palsy is a disorder of large term newborns delivered vaginally after a prolonged labor. Nerve compression against the sacrum during labor is more often the cause than is the misapplication of forceps. Children with forceps injuries, an unusual event, have forceps marks on the cheeks.


Clinical Features


The clinical expression of complete unilateral facial palsy in the newborn can be subtle and may not be apparent immediately after birth. Failure of eye closure on the affected side is the first noticeable evidence of weakness. Only when the child cries does flaccid paralysis of all facial muscles become obvious. The eyeball rolls up behind the open lid, the nasolabial fold remains flat, and the corner of the mouth droops during crying. The normal side appears paralyzed because it pulls and distorts the face; the paralyzed side appears to be normal. When paralysis of the facial nerve is partial, the orbicularis oculi is the muscle most frequently spared. In these injuries, the compression site is usually over the parotid gland, with sparing of nerve fibers that course upward just after leaving the stylomastoid foramen.


Diagnosis


The diagnosis of facial asymmetry is by observing the face of the crying newborn. Carefully examine the facial skin for laceration. Otoscopic examination is useful to establish the presence of hemotympanum. EMG does not alter the management of the palsy.


Management


Prospective studies regarding the natural outcome of perinatal facial nerve injuries are not available. Most authors are optimistic and indicate a high rate of spontaneous recovery. Such optimism may be appropriate, but its basis is only anecdotal experience. In the absence of data on long-term outcome, one cannot evaluate the efficacy of any suggested therapeutic intervention. Most newborns are not candidates for surgical intervention unless the nerve laceration occurs at delivery. In that event, the best response is to reconstitute the nerve if possible or at least to allow the proximal stump a clear pathway toward regeneration by debridement of the wound.


Immune-Mediated and Infectious Disorders


Postinfectious demyelination of the VII nerve is the cause of most cases of acute unilateral facial neuritis (Bell’s palsy) or bilateral facial neuritis. The basis for distinguishing a bilateral Bell palsy from the Guillain-Barré syndrome (acute inflammatory demyelinating polyneuropathy) is the preservation of limb tendon reflexes in Bell palsy. Discussion of the Guillain-Barré syndrome is in Chapter 7 .


Bell Palsy


Bell palsy is an acute, idiopathic, self-limited, typically monophasic, paralysis of the face caused by dysfunction of the facial nerve. The pathogenesis is believed to be viral (most often herpes simplex) but may also be postviral, immune-mediated, demyelination. The annual incidence is approximately 3/100, 000 in the first decade, 10/100, 000 in the second decade, and 25/100, 000 in adults. Only 1 % of cases have clinical evidence of bilateral involvement, but many have electrophysiological abnormalities on the unaffected side.


Clinical Features


A history of viral infection, usually upper respiratory, is recorded in many cases, but the frequency is not significantly greater than expected by chance. The initial feature of neuritis is often pain or tingling in the ear canal ipsilateral to the subsequent facial palsy. Pain accompanies facial weakness in 60 % of patients, impaired lacrimation in 60 %, taste changes in 30–50 %, and hyperacusis in 15–30 %.


Ipsilateral facial sensory symptoms are usually mild and explained by extension of inflammation from the facial nerve to the trigeminal nerve via the greater superficial petrosal nerve ( ). The palsy has an explosive onset and becomes maximal within hours. Either the child or the parents may first notice the palsy, which affects all muscles on one side of the face. Half of the face sags, enlarging the palpebral fissure. Weakness of the orbicularis muscle prevents closure of the lid. Efforts to use muscles of expression cause the face to pull to the normal side. Eating and drinking become difficult, and dribbling of liquids from the weak corner of the mouth causes embarrassment.


The most commonly affected portion of the nerve is within the temporal bone; taste, lacrimation, and salivation are impaired, and hyperacusis is present. However, examination of all facial nerve functions in small children is difficult, and precise localization is not critical to diagnosis or prognosis. The muscles remain weak for 2 to 4 weeks, and then strength returns spontaneously. The natural history of Bell palsy in children is not established, but experience indicates that almost all patients recover completely.


Diagnosis


Complete neurological examination is required in every child with acute unilateral facial weakness to determine whether the palsy is an isolated abnormality. Mild facial weakness on the other side or the absence of tendon reflexes in the limbs suggests the possibility of Guillain-Barré syndrome. Such children require observation for the development of progressive limb weakness.


Exclude possible underlying causes (e.g., hypertension, infection, and trauma) of facial nerve palsy before considering the diagnosis of Bell palsy. Examine the ear ipsilateral to the facial palsy for herpetic lesions (see the later discussion of Herpes Zoster Oticus). MRI shows contrast enhancement of the involved nerve, but acute, isolated facial palsy is not an indication for MRI in every child. A more reasonable approach is to watch the child and recommend an imaging study if other neurological disturbances develop or if the palsy does not begin to resolve within 1 month.


Management


Always protect the cornea if the blink reflex is absent and especially if the palpebral fissure remains open while sleeping. This may result in corneal ulcers due to prolonged ocular exposure and dryness. Ophthalmologic ointments are needed to prevent this complication. Patch the eye when the child is outside the home or at play, and apply artificial tears several times a day to keep the cornea moist. The use of corticosteroids has shown modest benefits in some reports; however, it is difficult to assess in children because their prognosis for complete spontaneous recovery is excellent. The clinician who elects to use corticosteroid therapy must first exclude hypertension or infection as an underlying cause.


Idiopathic Cranial Polyneuropathy


As the name implies, idiopathic cranial neuropathy is of uncertain nosology. The presumed mechanism is postinfectious, and many consider the syndrome an abortive form of the Guillain-Barré syndrome.


Clinical Features


Onset is usually in adults, and most childhood cases occur in adolescence. Similar cases described in infants subsequently developed limb weakness, and infantile botulism was the more likely diagnosis (see Chapter 6 ).


Constant, aching facial pain usually precedes weakness by hours or days. The pain is often localized to the temple or frontal region but can be anywhere in the face. Weakness may develop within 1 day or may evolve over several weeks. Extraocular motility is usually affected. Facial and trigeminal nerve disturbances occur in half of cases, but lower cranial nerve involvement is uncommon. Occasional patients have transitory visual disturbances, ptosis, pupillary abnormalities, and tinnitus. Tendon reflexes in the limbs remain active. Recurrent idiopathic cranial neuropathies occur as sporadic cases in adults but usually occur on a familial basis in children.


Diagnosis


The differential diagnosis includes the Guillain-Barré syndrome, infant and childhood forms of botulism, brainstem glioma, juvenile progressive bulbar palsy, pontobulbar palsy with deafness, and the Tolosa-Hunt syndrome. Preservation of tendon reflexes in idiopathic cranial polyneuropathy is the main feature distinguishing it from the Guillain-Barré syndrome. Prominent autonomic dysfunction and limb weakness separates botulism from idiopathic cranial polyneuropathy (see Chapter 6 , Chapter 7 ). Cranial nerve dysfunction in patients with brainstem glioma, juvenile progressive bulbar palsy, and pontobulbar palsy with deafness usually evolves over a longer period. The Tolosa-Hunt syndrome of painful ophthalmoplegia and idiopathic cranial polyneuropathy shares many features and may be a variant of the same disease process (see Chapter 15 ).


All laboratory findings are normal. The possibility of a brainstem glioma requires MRI of the brainstem in all cases. Examination of the cerebrospinal fluid occasionally reveals a mild elevation of protein concentration and a lymphocyte count of 5–6/mm 3 .


Management


The disease is self-limited, and full recovery is the expected outcome 2 to 4 months after onset. The use of corticosteroids is routine and believed to ease facial pain and shorten the course. The relief of pain may be dramatic, but evidence documenting a shortened course is lacking.


Genetic Disorders


Facioscapulohumeral Dystrophy


Facioscapulohumeral dystrophy (FSHD) sometimes begins during infancy as bilateral facial weakness (facial diplegia). Inheritance is by autosomal dominant transmission ( ). Approximately 70–90 % of individuals have inherited the disease-causing deletion from a parent, and the rest are de novo deletions. Offspring of an affected individual have a 50 % chance of inheriting the deletion. Prenatal testing is available.


Clinical Features


The onset of infantile FSHD is usually no later than age 5 years. Facial diplegia is the initial feature. When onset is early in infancy, the common misdiagnosis is congenital aplasia of facial muscles. Later, nasal speech and sometimes ptosis develop. Progressive proximal weakness begins 1 to 2 years after onset, first affecting the shoulders and then the pelvis. Pseudohypertrophy of the calves may be present. Tendon reflexes are depressed and then absent in weak muscle. Progression of weakness is often rapid and unrelenting, leading to disability and death from respiratory insufficiency before age 20 years. Typical features are a striking asymmetry of muscle involvement from side to side and sparing of bulbar extraocular and respiratory muscles. The weakness may also stabilize for long intervals and not cause severe disability until adult life.


Retinal telangiectasia and high-frequency hearing loss occurs in about half of affected families ( ). Both conditions are progressive and may not be symptomatic in early childhood.


Diagnosis


The diagnosis of FSHD is a possibility in every child with progressive facial diplegia. A family history of FSHD syndrome is not always obtainable because the affected parent may show only minimal expression of the phenotype. Molecular-based testing is reliable for diagnosis.


Myasthenia gravis and brainstem glioma are a consideration in infants with progressive facial diplegia. The serum concentration of creatine kinase is helpful in differentiating these disorders. It is usually elevated in the infantile FSHD syndrome and normal in myasthenia gravis and brainstem glioma. Electrophysiological studies show brief, small-amplitude polyphasic potentials in weak muscles, and a normal response to repetitive nerve stimulation.


Management


Treatment is supportive.


Juvenile Progressive Bulbar Palsy


Juvenile progressive bulbar palsy, also known as Fazio-Londe disease , is a motor neuron disease limited to bulbar muscles. Most cases are sporadic; autosomal recessive inheritance is the suspected means of transmission, but a rare autosomal dominant subtype may occur.


Clinical Features


Age at onset separates two clinical patterns. Stridor is the initial feature in early-onset cases (age 1 to 5 years). Progressive bulbar palsy follows, and respiratory compromise causes death within 2 years of onset. Respiratory symptoms are less common in later-onset cases (age 6 to 20 years). The initial feature may be facial weakness, dysphagia, or dysarthria. Eventually, the disorder affects all lower motor cranial nerve nuclei except the ocular motor nerve nuclei. Some children show fasciculations and atrophy of the arms, but limb strength and tendon reflexes usually remain strong despite severe bulbar palsy.


Diagnosis


The major diagnostic considerations are myasthenia gravis and brainstem glioma. MRI of the brainstem excludes brainstem tumors. EMG is useful to show active denervation of facial muscles, with sparing of the limbs and normal repetitive stimulation of nerves. Children with rapidly progressive motor neuron disease affecting the face and limbs may represent a childhood form of amyotrophic lateral sclerosis.


Pontobulbar palsy with deafness ( Brown-Vialetto-Van Laere syndrome ), a distinct disorder with phenotypic overlap, is characterized by a mixed upper and lower motor neuron bulbar palsy and deafness ( ).


Management


The disorder is often devastating. A previously normal child is no longer able to speak intelligibly or swallow. Feeding gastrostomy and a communication device are soon required. The child needs considerable psychological support. Treatment is not available for the underlying disease.


Oculopharyngeal Muscular Dystrophy


Autosomal dominant inheritance is the usual means of genetic transmission. The incidence is highest in families of French Canadian descent but the disorder is not restricted to any ethnic group. Mitochondrial myopathies account for cases with similar features not transmitted by autosomal dominant inheritance.


Clinical Features


Onset is usually in the fourth decade but may be as early as adolescence. The initial features are ptosis and dysphagia, followed by proximal weakness in the legs and external ophthalmoplegia. Eventually the disease affects all skeletal muscle, but spares smooth and cardiac muscle.


Many patients with oculopharyngeal muscular dystrophy also have EMG or biopsy evidence of denervation in the limbs. The neurogenic features may be attributable to neuronopathy rather than neuropathy, suggesting that this disorder is actually a spinal (bulbar) muscular atrophy.


Diagnosis


Definitive diagnosis relies on DNA testing. Muscle biopsy reveals a random variation in the size of the fibers, necrotic fibers, some fibrosis, and occasional internal nuclei. Autophagic vacuoles (rimmed vacuoles) and intranuclear fibrillary inclusion bodies are features common to OCPD, inclusion body myositis, and several hereditary distal myopathies/dystrophies. The presence of ragged-red fibers on histological examination of muscle indicates an underlying mitochondrial myopathy.


Management


The goal of therapy is symptom relief. Dietary changes help early dysphagia but gastrostomy is eventually required. Levator palpebral shortening may correct ptosis.


Osteopetrosis (Albers-Schönberg Disease)


The term osteopetrosis encompasses at least three hereditary skeletal disorders of increased bone density. Transmission of the most common form is by autosomal recessive inheritance (chromosome 11q). The features are macrocephaly, progressive deafness and blindness, hepatosplenomegaly, and severe anemia beginning in fetal life or early infancy. The calvarium thickens, and cranial nerves are compressed and compromised as they pass through the bone. The thickened calvarium may also impair venous return and cause increased intracranial pressure.


The main clinical features of the dominant form (1p) are fractures and osteomyelitis, especially of the mandible. Treatment with high-dose calcitrol reduces the sclerosis and prevents many neurological complications.


Melkersson Syndrome


Seven percent of facial palsies are recurrent. Autosomal dominant inheritance with variable expression is the suspected means of transmission in many cases. Some kindred members may have only recurrent facial nerve palsy, whereas others have recurrent neuropathies of the facial and ocular motor nerves. The Melkersson syndrome may be genetically distinct from other recurrent facial palsies with a gene locus at chromosome 9p11.


Clinical Features


Melkersson syndrome is a rare disorder characterized by the triad of recurrent facial palsy, lingua plicata, and facial edema. Attacks of facial palsy usually begin in the second decade, but the deeply furrowed tongue is present from birth.


The first attack of facial weakness is indistinguishable from Bell palsy except that a migraine-like headache may precede the attack. Subsequent attacks are associated with eyelid edema, which is soft, painless, nonerythematous, and nonpruritic. The edema is most often asymmetric, involving only the upper lip on the paralyzed side, but it may affect the cheek and eyelid of one or both sides. Cold weather or emotional stress may precipitate an attack of facial swelling. Lingua plicata is present in 30–50 % of cases. Furrowing and deep grooving on the dorsal surface of the tongue are permanent from birth. The transmission of this feature is by autosomal dominant inheritance but occurs as an isolated finding in some families.


Diagnosis


The diagnosis of Melkersson syndrome is established when two features of the triad are present. It is a consideration in any child with a personal or family history of recurrent facial palsy or recurrent facial edema. The presence of lingua plicata in any member of the kindred confirms the diagnosis. Histopathology of the affected eyelid reveals a granulomatous lymphangitis unique to the disease ( ).


Management


This disease has no established treatment.


Hypertension


Unilateral facial palsy may be a feature of malignant hypertension in children. The cause of the palsy is swelling and hemorrhage into the facial canal.


Clinical Features


The course of the facial paralysis is indistinguishable from that in Bell palsy. Nerve compression occurs in its proximal segment, impairing lacrimation, salivation, and taste. The onset coincides with a rise in diastolic blood pressure to greater than 120 mmHg, and recovery begins when the pressure reduces. The duration of palsy varies from days to weeks. Recurrences are associated with repeated episodes of hypertension.


Diagnosis


The occurrence of facial palsy in a child with known hypertension suggests that the hypertension is out of control.


Management


Control of hypertension is the only effective treatment.


Infection


The facial nerve is sometimes involved when bacterial infection spreads from the middle ear to the mastoid. External otitis may lead to facial nerve involvement by spread of infection from the tympanic membrane to the chorda tympani.


Diphtheria may cause single or multiple cranial neuropathies from a direct effect of its toxin. Facial palsy, dysarthria, and dysphagia are potential complications. Basilar meningitis, from tuberculosis or other bacterial infections, causes inflammation of cranial nerves as they leave the brain and enter the skull. Multiple and bilateral cranial nerve involvement is usually progressive.


Herpes Zoster Oticus (Ramsay Hunt Syndrome)


Herpes zoster infection of the geniculate ganglion causes herpes zoster oticus.


Clinical Features


The initial feature is pain in and behind the ear. This pain is often more severe and persistent than that expected with other causes of Bell palsy. Unilateral facial palsy, indistinguishable from Bell palsy by appearance, follows. However, examination of the ipsilateral ear, especially in the fossa of the helix and behind the lobule, shows a vesicular eruption characteristic of herpes zoster. Hearing loss is associated in 25 % of cases.


Diagnosis


The only historical feature distinguishing herpes zoster oticus from Bell palsy is the severity of ear pain. Examination of the ear for vesicles is critical to the diagnosis.


Management


Herpes zoster infections are usually self-limited but painful. A combination of oral acyclovir, 800 mg five times a day for 7 days, and oral prednisone, 1 mg/kg for 5 days and then tapered, improves the outcome for facial nerve function in people 15 years and older ( ). Complete recovery occurs in 75 % of those treated within 7 days of onset and in 30 % treated after 7 days. The varicella vaccine may reduce the incidence of new cases and decrease the severity of symptoms ( ).


Sarcoidosis


Cranial nerve dysfunction is the most common neurological complication of sarcoidosis. Basilar granulomatous meningitis is the usual cause ( Figure 17-2 ), but the facial nerve may also be involved when parotitis is present.


Mar 3, 2019 | Posted by in NEUROLOGY | Comments Off on Lower Brainstem and Cranial Nerve Dysfunction
Premium Wordpress Themes by UFO Themes