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Q1: What disease process are the x ray and MRI findings diagnostic of?
The differential diagnosis of an acute monoarthritis includes a pyogenic infection of the joint. Tuberculosis should also be considered in an individual who is PPD positive even with a normal chest radiograph. The resorption of the humeral head with a sharp line of demarcation, almost as if surgically excised, is diagnostic of this disease. Shards of bone can sometimes be identified in the soft tissue and was noted in a computed tomogram and MRI of the shoulder (not shown). This picture is very characteristic of the atrophic form of a neuropathic arthropathy of the shoulder1 with the most common cause being syringomyelia. The MRI (fig 2; see p 374) confirms the diagnosis of syringomyelia with a large syrinx in the spinal cord and all cultures were negative.
Q2: What are the other causes of osteolysis?
The causes of osteolysis are shown in box 1.
Box 1: Causes of osteolysis
Reflex sympathetic dystrophy.
Indirect—for example, leprosy.
Collagen vascular diseases
Rheumatoid arthritis, usually the lateral end of the clavicle.
Chronic renal failure
Q3: What are the other clinical features of this disease?
Syringomyelia can be associated with Chiari I and II malformations, Dandy-Walker malformation, and basilar invagination. Frequently, the signs and symptoms in children and adolescents may include scoliosis, dissociated sensory loss, neck pain, vomiting, and lower motor neuron signs in the upper limbs. In adults, the clinical presentation is more variable, but usually point towards dysfunction of the cervical cord. It is worth noting that the classic “dissociated sensory loss” is present in only 49% of patients with a syrinx.2 More commonly, lower motor neuron signs are seen in the upper limbs and long tract signs are seen in the lower limbs. Other findings include dizziness, nystagmus, scoliosis, and even brain stem symptoms like dysphagia, facial numbness, and vertigo when there is extension of the syrinx into the medulla.
Syringomyelia is a cavitation within the spinal cord appearing in the third to fourth decade. Familial cases have also been described.3 The Arnold-Chiari malformation with herniation of the cerebellar tonsil is found in more than two thirds of patients. It may also be a late consequence of spinal cord trauma, with delayed onset observed in 5% leading to an ascending spinal syndrome. As a result of arachnoiditis, cerebrospinal fluid circulation is impaired. The syrinx mainly in the lower cervical region interrupts decussating spinothalamic fibres leading to a loss of pain and temperature in a shawl-like distribution with preservation of light touch, vibration, and proprioception. Painless ulcers of the fingers may be a presenting feature. Extension of the syrinx into the anterior horn results in a loss of motor neurons and an amyotrophy. It begins in the small muscles of the hand with asymmetric weakness and early loss of muscle stretch reflexes in arms. Extension into the lateral columns results in lower extremity spasticity, paraparesis, brisk tendon reflexes, and a positive Babinski sign.
Key learning points
Recognise the radiographic appearance of osteolysis and know its causes.
The most common cause of a neuropathic joint of the shoulder is syringomyelia.
Resorption of the head of the humerus is a characteristic radiographic finding of syringomyelia.
Patients may present with an acute enlargement of the shoulder with destruction of the head of the humerus. Remarkable subcutaneous oedema of the hands referred to as “main succulente” has been described. Interruption of the central autonomic pathways results in hyperhydrosis. Resorption of the head of the humerus with a well defined margin is a characteristic radiographic finding of syringomyelia.
Syringomyelia with resorption of the humeral head representing a neuroarthropathy