36. Friedreich’s Ataxia
Definition
Friedreich’s ataxia is an ataxia inherited via an autosomal recessive gene. This is the most common autosomal recessive form of ataxia, accounting for about half of all hereditary ataxia cases.
Incidence
The incidence of Friedreich’s ataxia is estimated at 1:22,000 to 1:50,000, predominately in populations of Europeans and North Americans of European descent. This disorder is virtually nonexistent among African and Asian populations.
Etiology
Friedreich’s ataxia is produced by a mutation at the 9q13-21.1 location of chromosome 9, which results in excessive repetitions of the DNA sequence guanine-adenine-adenine (GAA). The onset and length of time until the patient is unable to ambulate is determined by the number of GAA repetitions within the mutation.
Signs and Symptoms
• Absent lower extremity deep tendon reflexes
• Areflexia
• Cardiac enlargement
• Deafness
• Dementia (uncommon)
• Diabetes mellitus
• Difficulty standing and running
• Dysarthria
• Dysphagia
• Facial muscle weakening
• Foot deformity
• Foot inversion
• Hammertoes
• Heart block
• High plantar arches
• Hypertrophic cardiomyopathy
• Incoordination of breathing, speaking, swallowing, and laughing
• Kyphosis
• Mental retardation (uncommon)
• Myocardial fibrosis
• Myocarditis
• Nystagmus
• Pes cavus
• Pes varus
• Progressive cardiac failure
• Progressively slow and clumsy walking
• Psychosis (uncommon)
• Scoliosis
• Swallowing weakness
• Systolic ejection murmurs
• Tachycardia
• Ventricular hypertrophy
Medical Management
The prognosis for the patient with Friedreich’s ataxia is not promising. No reported treatment regimens are known to alter the progressively detrimental neurologic nature of this disease. Present treatment regimens are oriented toward associated systemic problems, such as heart failure, cardiac dysrhythmias, or diabetes mellitus.
Surgical interventions are essentially palliative in nature. Surgical correction of scoliosis or deformities of a foot (or feet) may be undertaken in a select few patients to lessen their discomfort and ease respiratory symptoms brought on by the scoliosis. No definitive surgical option produces a cure for Friedreich’s ataxia or halts the progression.
The disease generally lasts 15 to 20 years. Patients generally survive to age 25 to 30 years. The typical age of onset is between 8 and 15 years old. Occasionally, a patient with Friedreich’s ataxia who does not have heart disease or diabetes mellitus may survive into the sixth or seventh decade of life, but that is the exception rather than the rule.
Complications
• Cardiomyopathy
• Congestive heart failure
• Infections
• Kyphoscoliosis
• Pes cavus
• Pressure sores
Anesthesia Implications
Pulmonary assessment is a crucial preoperative task along with cardiac evaluation. Restrictive pulmonary disease frequently develops in association with Friedreich’s ataxia. Cardiomyopathy is also frequently seen in Friedreich’s ataxia. The choice of volatile agent for the patient will be heavily influenced by the degree of cardiac and pulmonary dysfunction. It is desirable to use an agent that relaxes the bronchial smooth muscles, such as sevoflurane. Hemodynamic support is highly desired, such as is provided by desflurane. Positive pressure ventilation for the patient with Friedreich’s ataxia must take into account the lack of lung compliance resulting from the disease. Reduced inspiratory pressures along with prolonged expiratory phases will reduce the risk of pulmonary injury.
The effects of nondepolarizing muscle relaxants have been reported to be altered by this disease process. The anesthetist must be mindful of the similarities of this disease process to other motor neuron degeneration diseases. Typically both onset and recovery from nondepolarizing muscle relaxants will at first appear to be within the expected limits; however, preoperative preparation should be made for prolonged ventilatory support for the patient because of the probable residual effects of any muscle relaxants following the surgical procedure.
Regional anesthesia techniques have been reported to be effective in patients with Friedreich’s ataxia without exacerbating neurologic symptoms.
The anesthetist should anticipate and expect any of a variety of cardiac dysrhythmias as a result of the high degree of associated cardiomyopathies, particularly hypertrophic myopathies.
