Laboratory Studies
See the list below:
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Pulmonary function tests, especially vital capacity, should be ordered on any patient with symptoms or suggested respiratory impairment. Serial studies are useful to document and monitor for progression.
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No specific laboratory blood studies have proven useful in the diagnosis or monitoring of PTS.
Imaging Studies
See the list below:
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Magnetic resonance imaging (MRI), myelography-enhanced computed tomography (CT-myelography), and plain radiography of the spine are useful in the diagnosis and management of PTS.
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MRI is the preferred initial imaging study for the diagnosis of PTS. Most PTS develops around the site of the original spinal cord lesion. T1 and T2 sequences provide differentiation between CSF and normal spinal cord tissue and areas of spinal cord edema, myelomalacia, or gliosis. Serial examinations are necessary to evaluate for changes in cavity size over time; there is a marked lack of correlation between cavity size and severity of clinical symptoms. (See images below.)
T1-weighted magnetic resonance imaging (MRI) scan of a slender syrinx (arrow) extending from the C5 vertebral level. This syrinx extends beyond the image to an area of spinal cord disruption at the T3 vertebral level.
Same patient as in image above, with the magnetic resonance imaging (MRI) scan slightly farther down the cervicothoracic region of the spine
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CT-myelography delineates the extent of the syrinx cavity, arachnoid scarring, and tethering of the spinal cord. This study demonstrates the extent of obstruction to CSF flow.
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Radiographs of the spine delineate spinal deformities such as fractures, dislocations, and abnormal spinal kyphotic or lordotic changes. Flexion/extension views assist in evaluation of spinal stability.
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Ultrasonography may be used intraoperatively after laminectomy to visualize syrinx cavities and septations.
Other Tests
See the list below:
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Serial quantitative strength measurements including pinch and grip tests or hand-held myometry are useful in confirming progression of weakness.
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Calculation of the central motor conduction time using motor evoked potentials is useful in monitoring PTS; however, this technique is not widely available.
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Standard electromyographic techniques, including nerve conduction studies, F-wave latencies, and needle electromyography (EMG), are less sensitive and specific in detecting PTS. Needle EMG may demonstrate a variety of abnormalities, including continuous motor unit activity, synchronous motor unit potentials, myokymic discharges, segmental and propriospinal myoclonus, and respiratory synkinesis. However, as these studies are best used to exclude other causes for the person's symptoms.
Histologic Findings
On pathologic section, cavitation of the gray matter is seen within the spinal cord. This phenomenon may involve the central canal or may be located eccentrically. An inner layer of gliotic tissue usually is present. The gray matter between the dorsal horns and posterior columns often is involved, possibly because of its relative avascularity and lack of connective tissue. Multiple cyst cavities, separated by complete or partial septae, are often present.
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This illustration shows a T1-weighted, cervical magnetic resonance imaging (MRI) scan of multiple syrinx cavities (arrows). Note the lowest thin cavity extending into the thoracic spinal cord.
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This T2-weighted magnetic resonance imaging (MRI) scan (same patient as above) delineates the syrinx cavity. Note the spinal cord edema extending rostrally from the upper limit of the cavity.
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T2-weighted magnetic resonance imaging (MRI) scan (same patient as above) after patient underwent expansile duraplasty. Note dramatic reduction in size of the main syrinx cavity (white).
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T2-weighted sagittal image of large, multiloculated cervical syrinx extending into brainstem. Patient had preserved functional status.
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T1-weighted magnetic resonance imaging (MRI) scan of a slender syrinx (arrow) extending from the C5 vertebral level. This syrinx extends beyond the image to an area of spinal cord disruption at the T3 vertebral level.
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Same patient as in image above, with the magnetic resonance imaging (MRI) scan slightly farther down the cervicothoracic region of the spine
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T2 proton density magnetic resonance imaging (MRI) scan demonstrating syrinx cavity (arrow) extending from approximately C6-C7 to T2. The syrinx cavity is 9 mm at its widest dimension. The spinal cord is reduced to a thin membrane at this level and is atrophic below.
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T1-weighted image demonstrating a large, multiloculated cervical syrinx cavity. This is a recurrent syrinx, having come back despite an attempt at drainage utilizing expansile duraplasty.
