The particular muscle groups that are affected on the two sides may vary. Exceptionally, motor function is spared, and the segmental dissociated sensory loss and/or pain are the only marks of the disease. In a few of the cases, especially those with the Chiari malformation, the reflexes in the arms are preserved or even hyperactive, as might be expected with upper rather than lower motor neuron involvement. Or the shoulder muscles may be atrophic and the hands spastic. In the lower extremities the weakness, if present, is of a spastic (corticospinal) type.
The characteristic segmental sensory dissociation is usually bilateral but a unilateral pattern affecting only one hand and arm is not unknown, and this is true of the amyotrophy as well. The sensory loss is distributed in a “cape” or hemicape pattern, often extending to back of the head or the face and onto the trunk. Although tactile sensation is usually preserved, there are cases in which it is impaired, usually in the region of the densest analgesia over the trunk or hand. Exceptionally there is no sensory loss in the presence of amyotrophy, and cases have been recorded in which only a hydrocephalus and hydromyelia were present with spastic paraparesis. If tactile sensation is affected in the arms, joint position and vibratory sense tend also to be impaired. In the lower extremities and over the abdomen there may be some loss of pain and thermal sensation proximally, but more often there is a loss of vibratory and position sense, which is indicative of a posterior column lesion and is the basis of ataxia. A Horner syndrome may result from ipsilateral involvement of the intermediolateral cell column at the C8, T1, and T2 levels.
Pain has been a symptom in about half of our patients with developmental types of syringomyelia. The pain is usually unilateral or more marked on one side of the neck, shoulder, and arm; it is of a burning, aching quality, mostly in or at the border of areas of sensory impairment. In a few patients, it involves the face or trunk. An aching pain at the base of the skull or posterior cervical region that is intensified by coughing, sneezing, or stooping (brief exertional pain) is often present, but, as Logue and Edwards point out, pain of this type may be a feature of Chiari malformation without syringomyelia and in that case is probably attributable to compression or stretching of cervical roots.
Syringobulbia is the lower brainstem equivalent of syringomyelia. Usually the two coexist and the brainstem cavity is simply an extension of one in the upper cord, but occasionally the bulbar manifestations precede the spinal ones or, rarely, occur independently. The glial cleft or cavity is located most often in the lateral tegmentum of the medulla, but it may extend into the pons and, rarely, even higher. The symptoms and signs are characteristically unilateral and consist of nystagmus, analgesia, and thermoanesthesia of the face (numbness); wasting and weakness of the tongue (dysarthria); and palatal and vocal cord paralysis (dysphagia and hoarseness). Diplopia, episodic vertigo, trigeminal pain or facial sensory loss, and persistent hiccough are less common symptoms. For understandable reasons, the diagnosis of brainstem MS is often raised. The clinical and pathologic features of syringobulbia have been described in great detail by Jonesco-Sisesti.