Management of patients with congenital myopathies with particular emphasis on respiratory support

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The degree of respiratory involvement in the congenital myopathies depends on the precise diagnosis. This has been outlined in the individual sections. Respiratory failure can occur at any age in a patient with a congenital myopathy, including adulthood. It can happen slowly, but more alarmingly, can be sudden and catastrophic. The latter often, but not always, happens in the setting of an intercurrent respiratory tract infection. The likelihood of respiratory compromise cannot be judged from muscle strength elsewhere in the body, as the weakness of the intercostal muscles and diaphragm can be out of proportion. Therefore, surveillance is vitally important, and is best done by a respiratory physician as part of a multidisciplinary team. Comprehensive guidelines for the assessment of respiratory function in congenital neuromuscular disorders were outlined during the 117th ENMC workshop, and are recommended reading (Wallgren-Pettersson et al., 2004b). The focus is on

Table 1.3

Magnetic resonance imaging findings in genetically proven congenital myopathies

Magnetic resonance imaging findings in genetically proven congenital myopathies

Table 1.3

Nemaline myopathy

Nemaline myopathy

CFTD (mutation

Region

secondary to ACTA1

secondary to NEB

RYR1

unknown)

Anterior thigh

Diffuse involvement of

Mild: no abnormality

AM > AL

Mild diffuse changes;

all muscles; S > G

Moderate: RF = severe;

vasti > RF VL > RF

mostly seen in VL

VL, VI > VM

S > G

S, G, adductors = mild

Posterior thigh

Diffuse involvement,

Mild: no abnormality

Less affected than

Diffuse changes, less

without selectivity

Moderate-severe

anterior thigh SM > ST

than anterior muscles; sparing of G; ST less affected

Lower leg

Diffuse involvement,

Mild: TA and soleus

Changes less in anterior

Not reported

with relative sparing

selectively involved,

posterior; Soleus >

of the soleus

TP and gastrocnemius relatively spared Moderate: diffuse involvement particularly of the soleus

gastrocnemius Lateral gastrocnemius > medial Peroneal > TA

Limb girdles

Not reported

Not reported

Not reported

Increased fat and atrophy, proportional to duration of disease; particular involvement of lumber paraspinal muscles

RF: rectus femoris; VL: vastus lateralis; VI: vastus intermedius; VM: vastus medialis; S: sartorius; G: gracilis; TA: tibialis anterior; TP: tibialis posterior; gastroc: gastrocnemius; AM: adductor magnus; AL: adductor longus; SM: semimembranosus; ST: semitendinosus.

RF: rectus femoris; VL: vastus lateralis; VI: vastus intermedius; VM: vastus medialis; S: sartorius; G: gracilis; TA: tibialis anterior; TP: tibialis posterior; gastroc: gastrocnemius; AM: adductor magnus; AL: adductor longus; SM: semimembranosus; ST: semitendinosus.

detecting change in respiratory muscle strength, ability to cough, overnight oximetry and the presence of subtle symptoms of sleep-disordered breathing. This allows safe prediction of the development of respiratory failure. Most patients will show restriction of their respiratory capacity, even if they are symptom-free. In addition, weak airway muscles can lead to obstructive sleep apnea, further complicating nocturnal hypoventilation. For this reason, overnight sleep studies are recommended.

The need for ventilatory support in congenital myopathies can be either intermittent or constant, and during the day or night or both. The need to intervene can be in the acute situation, as well as in the long term. Respiratory tract infections are the commonest cause of hospital admission and death in patients with neuromuscular disorders (Bach et al., 1997). There is evidence, although only anecdotal at this stage, that physiotherapy-assisted coughing may play a key part in preventing the build-up of secretions, and thus reduce the occurrence and severity of respiratory tract infections (Wallgren-Pettersson et al., 2004b). This needs to be studied further. It seems that non-invasive ventilation is very effective in these patients, and a clear consensus exists that ventilatory support is successful in the congenital myopathies. Detailed recommendations as to the timing and type of support are outlined in the ENMC guidelines (Wallgren-Pettersson et al., 2004b).

Bulbar muscle involvement predisposes patients to aspiration of secretions, food, and stomach contents. This can precipitate respiratory deterioration. Also, swallowing difficulties lead to nutritional deficiencies, weight loss, subsequent increased susceptibility to infection, and constipation. The neonatal period is the time when swallowing difficulties are most prominent, sometimes necessitating gavage feeding. These difficulties improve in 50% of infants (Ryan et al., 2001). If they do not improve, or difficulties intervene later, assessment by a speech therapist as part of a multidisci-plinary team is required. Insertion of a gastrostomy tube may be beneficial.

Treatment of joint contractures and scoliosis is best undertaken by a specialized team, including physiotherapist, orthotist, and orthopedic surgeon. Aggressive physiotherapy of joint contractures, including splinting and

Vastus Lateralis Atrophie
Fig. 1.16. Magnetic resonance imaging in chromosome 15 rod-core disease. This shows symmetrical fatty atrophy of the vastus lateralis (arrow), intermedius and medialis muscle bilaterally, with sparing of the rectus femoris, hamstring and adductor muscles.

serial casting, should be the initial treatment. However, if contractures do not respond to this treatment, surgery should be considered, especially if it will assist the child to improve function or mobility. Treatment options for scoliosis include bracing and spinal fusion.

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