In 1546, Esteinne first described this disease. Charles was the first to name it syringomyelia, a chronic progressive disorder affecting the spinal cord, classified as a congenital developmental spinal anomaly characterized by cavity formation. The clinical features include muscle atrophy, loss of pain and temperature sensation in corresponding segments with preserved touch and proprioception, limb paralysis, and trophic disturbances.

bubble_chart Etiology

Greenfield emphasized that syringomyelia is characterized by tubular cavities in the spinal cord, extending over many segments from the cervical region, and should be distinguished from simple cysts of the central canal. Hydromyelia is more appropriate for the latter. He proposed that this condition results from developmental malformations of the dorsal midline of the spinal cord. The syrinx cavity may communicate with the central canal, and the lining of the cavity may show ependymal cells, with fluid inside resembling CSF. Others suggest that the disease is caused by glial cell proliferation, with central necrosis leading to cavity formation.

bubble_chart Pathological Changes

Cavities are mostly confined to the cervical spinal cord and can extend along the entire length of the spinal cord. Their cross-sectional area varies in different segments, reaching the maximum extent in the cervical cord and cervical enlargement. Initially, the cavities are limited to the base of the posterior horn or the anterior commissure of the spinal cord. The cysts gradually enlarge, involving more gray and white matter on both sides. Sometimes, only a narrow rim of spinal cord parenchyma remains, with neural tissue degenerating and disappearing. The cavities may extend into the medulla oblongata, but rarely reach the brain marrow.

The age of onset is between 31 and 50 years, with rare occurrences in children and the elderly. Males are more affected than females, and there have been reports of family history. The progression is slow and lasts for many years. Symptoms are related to the affected segment and its location within the neural axis. Lesions in the lower cervical and upper thoracic segments are more common.

(1) Sensory Symptoms: Pain and temperature sensations are lost due to the interruption of the spinothalamic fibers, while light touch, tremor sensation, and position sense are relatively preserved because the posterior columns are not affected early on. This is a characteristic feature of the disease, known as segmental dissociated sensory loss. Deep pain may occur, involving the shoulders and arms. When the posterior columns are affected, corresponding deep sensory impairments appear.

(2) Motor Symptoms: If the lesion extends to the anterior horn cells, it causes destruction of motor neurons, leading to paralysis, atrophy, reduced muscle tone, muscle fiber tremors, and loss of reflexes in the corresponding muscles. The intrinsic hand muscles are usually the first to be affected, followed by the forearm, upper arm, and shoulder girdle. Severe involvement of the hand muscles may result in a claw-hand deformity. If the lateral columns are affected, the lower limbs may exhibit symmetric or asymmetric spastic paresis, hyperreflexia, and metatarsal extensor responses. In advanced stages, Horner's sign may appear due to damage to the sympathetic neurons in the intermediolateral cell column.

(3) Trophic Disorders: Due to trophic disturbances in joint cartilage and bone, as well as dysregulation of feedback mechanisms caused by impaired deep and superficial sensations, Charcot joints may develop. These are characterized by joint swelling, effusion, excessive mobility, and painless crepitus during movement. X-rays reveal destruction and fragmentation of the articular cartilage and bone ends, sometimes with subluxation. The skin may exhibit profuse sweating, anhidrosis, discoloration, hyperkeratosis, rough and brittle nails. Painless ulcers may also occur. Scoliosis or kyphosis of the thoracic spine is common. Bladder and rectal sphincter dysfunction are often seen in advanced stages. If the lesion extends to the medulla oblongata, it may cause dysphagia, tongue muscle atrophy and paralysis, and nystagmus, which can be life-threatening. CSF examination is mostly normal, and Queckenstedt's test rarely shows obstruction.

MRI examination: The cavity appears as a low signal, visible along the longitudinal axis of the spinal cord in the sagittal plane, while the transverse plane clearly shows the size and shape of the cavity at the corresponding level. MRI holds significant diagnostic value for this condition.

bubble_chart Differentiation

In the early stages of this disease, there is atrophy and weakness of the intrinsic hand muscles, as well as impaired pain and temperature sensation. The limbs may exhibit mild upper motor neuron paralysis, which requires careful differentiation from the spinal type of cervical spondylosis, especially since adults often show signs of cervical arthropathy on plain X-rays, making it more easily confused. However, this disease often presents with segmental dissociated sensory disturbances, widespread atrophy of the hand and upper limb muscles, and more severe neurotrophic disturbances compared to cervical spondylosis. Cervical spondylosis does not involve bulbar symptoms, and the chance of Queckenstedt test obstruction is higher in syringomyelia than in cervical spondylosis. If diagnosis is difficult, MRI can provide a definitive diagnosis.

The joint swelling and lesions of the articular cartilage and subchondral bone caused by syringomyelia-related Charcot joints need to be differentiated from other joint diseases, such as rheumatoid arthritis, osteoarthritis, and joint subcutaneous nodules. The characteristics of this disease include joint swelling and osteochondral destruction with relatively little pain.