Pediatric Peroneal Muscular Dystrophy

Introduction to pediatric skeletal muscle atrophy Peronialmyoatrophy, also known as Charcot-Marie-Tooth disease (CMT), is the most common group of peripheral neuropathies, accounting for approximately 90% of all hereditary neuropathies. The common features of this group of diseases are children or adolescents with chronic progressive iliac muscle atrophy. Symptoms and signs are relatively symmetrical. Most patients have a family history. This disease was first reported by Charcot, Marie and Tooth in 1886, so it is also called Charcot- Marie-Tooth (CMT) disease, also known as sacral muscle atrophy (peronealmyoatrophy) due to the main clinical features of iliac muscle atrophy. Although Dyck proposed the use of hereditary motor neuropathy (HMSN) as the official name for this group of diseases, most of the literature is still accustomed to using CMT. According to neurophysiological and neuropathological findings, CMT is classified into type I and type II, CMTI type is called hypertrophic type, and type CMTII is called aneuronal type. basic knowledge The proportion of illness: 0.0003% - 0.0005% Susceptible people: children Mode of infection: non-infectious Complications: muscle atrophy

Causes of sacral muscular atrophy in children

(1) Causes of the disease

Most of CMT is autosomal dominant inheritance, and a small part is autosomal recessive inheritance, X chromosome linked dominant inheritance and X chromosome linked recessive inheritance.

(two) pathogenesis

Genetic mode

(1) CMTI type: It can be autosomal dominant, recessive and X-linked dominant or recessive. In recent years, CMTI type is divided into IA type, IB type and IC type, and CMTIA type is the most. Common (56% to 60%), caused by mutation of PMP-22 gene on autosome 17P11.2-12, rare CMTIB type (30%), pathological gene in Iq21-23, and myelin protein P0 (MPZ) gene Mutation-related, IC-type pathological genes are still unknown, X-linked pathological genes are in Xq13-1, (2) CMTII type: There are three types of inheritance, usually autosomal dominant, recessive and X-linked inheritance, the disease The autosomal dominant pathological gene is unknown in Ip35-36, and the Chang and X-linked pathological genes are unknown.

2. Pathological changes

(1) CMTI type: CMTI type sural nerve biopsy results are mainly large, the number of medium-diameter fibers is significantly reduced, collagen in the bundle is proliferated, and the density of myelin fibers is progressively decreased with age, demyelination is aggravated, due to return Segmental demyelination and remyelination are enhanced. Schwann cell hyperplasia and neuroendosome components form a concentric "onion ball"-like structure around the axon, and the spinal cord is degenerated, and the thin beam is more pronounced than the wedge bundle.

(2) CMT type II: CMT type II sural nerve pathology is mainly axonal degeneration, demyelinating is not significant, Schwann cell proliferation is "onion ball" change and rare.

Pediatric sacral muscle atrophy prevention

Prenatal examination, first determine the genotype of the parents, and then use the fetal villi, amniotic fluid or cord blood to analyze the fetal genotype, to make prenatal diagnosis, in order to terminate the pregnancy in time.

Pediatric dystrophic complications Complications muscle atrophy

High arch, foot drop, hammer or claw-shaped toe can occur, and there may be sensory disturbances. Deep feelings often show gait instability or closed eyes in the dark, and the posterior side of the spine is deformed.

Symptoms of sacral muscle atrophy in children Common symptoms Powerless gastrocnemius muscle strain gait instability, closed eyes, difficult to sign muscle atrophy, spinal cord atrophy, sensory disturbance, hand deformity

1. Tibial muscle atrophy type I occurs in childhood or adolescence, about 2/3 cases occur before the age of 10, but it has also been reported that people under 1 year old or after birth often show poor motor development, more men than women See, the age of the disease in the same family and the severity of the disease have a large variation, women have mild symptoms, have seen a family of 5 children, the first child (female), the third child (female), The fifth child (male) was born in 4 to 5 years old, as shown in Figure 1. The other two children were not sick. The early symptoms showed the beginning of the lower extremities, the lower limbs were weak, the walking and running were difficult, and the muscle atrophy was often Starting from the tibia toe total muscle and small muscles of the foot, then the tibialis anterior muscle atrophy and gradually develop, the muscle atrophy generally does not exceed 1/3 of the lower thigh, so the thigh and calf form a sharp contrast, due to the atrophy of the foot muscle, can appear High arch, foot drooping, hammer-shaped or claw-shaped toe, patients can have a gait, generally involving the hand and forearm muscles in the late stage, the fingers can not be straight, the fine movement is difficult to complete, and the upper arm develops normally, the muscle atrophy progresses Very slow, some children may have sensory disturbances Deep feeling is often manifested in black days when gait is unstable or closed eyes are difficult to sign positive. Some patients have cold limbs, less sweat or cyanosis, early reflexes disappear, and then other tendon reflexes are successively weakened or disappeared, and posterior tibial deformity About 10% of cases were met.

2. The type II of sacral muscle atrophy is late, about 2/3 cases develop after 10 years old, the progress is slow, the muscle atrophy and weakness are lighter than CMTII type, and the sensory disturbance is not as obvious as type I.

Examination of pediatric skeletal muscle atrophy

1. Cerebrospinal fluid examination increased the protein content of cerebrospinal fluid in half of children with CMTI type.

2. Muscle biopsy showed that muscle biopsy showed neurogenic muscle atrophy. The peripheral nerve changes of CMTI type in nerve biopsy were mainly the onion head-like changes in demyelinating and Schwann cell proliferation; CMT type II was mainly axonal degeneration.

Abnormal brainstem auditory evoked potentials and visual evoked potentials in patients with X-linked dominant dominant genes, and somatosensory evoked potentials and peripheral conduction velocity slowed down.

Neurophysiological examination showed that the motor and sensory nerve conduction velocity slowed down, which is an important electrophysiological feature of the disease. The peripheral nerve conduction velocity (NCV) of the infant is lower than the normal value of more than 60%, and the NCV of the infant older than 3 years old is less than 38m/s. The CMT type II peripheral nerve action potential amplitude is <80% of the normal low limit, and the nerve conduction velocity is lower or slightly slower than the normal value.

Diagnosis and diagnosis of sacral muscle atrophy in children

diagnosis

The diagnosis of hereditary motor sensation peripheral neuropathy mainly depends on genetic family history, clinical features, neurophysiological examination and nerve biopsy. Molecular genetic analysis can also be used for diagnosis when conditions are available.

Chronic motor sensory neuropathy in children or adolescents should consider the possibility of this disease, according to the onset of adolescent insidious, progressive lower extremity muscle atrophy, and a special distribution form (limited to the lower third of the thigh, presented "Crane legs"), but the muscle strength is relatively good, the tendon reflex often weakens or disappears, the sleeve type sensory disturbance and other characteristics, the diagnosis is not difficult, a positive family history can help diagnose.

Differential diagnosis

The disease should be differentiated from chronic inflammatory demyelinating polyneuropathy (CIDP), distal spinal muscular atrophy and distal progressive muscular dystrophy.

1. Chronic progressive distal spinal muscular atrophy The muscle atrophy and muscle weakness of the disease and the course of the disease are similar to CMT disease, but the sensory function is not tired, and EMG shows anterior horn damage.

2. Chronic Guillain-Barré syndrome progresses relatively quickly, most of the muscle atrophy is lighter, CSF can be seen in protein-cell separation, and prednisone is better.

3. Distal myodystrophy Clinical manifestations are similar to CMT II, but EMG shows that myogenic damage can be identified.

4. Familial amyloid polyneuropathy is difficult to distinguish clinically from CMT and requires nerve biopsy or DNA analysis.

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