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AJNR - American Journal of Neuroradiology

A, Sagittal T1-weighted image (600/8/2) shows a Chiari I malformation, with tonsillar herniation to the mid-C2 level and a pointed configuration to the cerebellar tonsils (arrow).

B, Sagittal T2-weighted image (3000/105_eff /3) shows T2 prolongation within the spinal cord parenchyma at the C2–C3 level.

C, Sagittal images from a cine phase-contrast flow study in systole (left panel) and diastole (right panel), sensitized to flow in the superior-to-inferior direction (see text for parameters). Note the absence of flow-related phase change at the level of the foramen magnum, as well as prominent tonsillar motion in both systole and diastole, with the curved arrows indicating the position of the tonsillar tips in systole and diastole. Subtle linear low signal is present anterior to the tonsil in diastole (right panel, straight arrow), indicating minimal flow between the fourth ventricle and the spinal subarachnoid space below the level of the foramen magnum.

D, Sagittal T1-weighted image (500/14/3) obtained 6 weeks later after limited extradural decompression of the foramen magnum. Cord expansion and parenchymal hypointensity (curved arrows) are present in the upper cervical cord.

E, Sagittal T2-weighted image (3000/105_eff /3) corresponding to D shows marked upper cervical cord T2 prolongation. This was presumed related to ongoing or increased obstruction to CSF flow.

F, Axial T1-weighted image (500/13/2) shows that the central parenchymal signal abnormality is somewhat ill-defined and not as low in signal intensity as CSF.

G, Cine phase-contrast flow study sensitized to motion in the superior-to-inferior direction (see text for parameters) shows prominent downward motion of the brain stem and cerebellar tonsils (which appear white), but no definite flow of CSF at the foramen magnum. The tip of the tonsil is indicated (curved arrow).

H, Sagittal T1-weighted image (600/8/2) after aggressive decompression of the foramen magnum, including duraplasty, lysis of arachnoid adhesions, and partial tonsillar resection shows that the upper cervical cord appears to be of normal caliber. Minimal parenchymal hypointensity persists in the upper cervical spinal cord (curved arrow).

I, Sagittal T2-weighted image (4000/105_eff /2) corresponding to H shows near-complete resolution of previously seen abnormal T2 prolongation.

J, Cine phase-contrast flow study sensitized to motion in the superior-to-inferior direction (see text for parameters) no longer shows abnormal downward motion of the brain stem or residual cerebellar tonsils. CSF flow is evident at the foramen magnum (curved arrows).

A, Midline sagittal T2-weighted image (4000/102_eff /2) shows central T2 prolongation within the lower cervical spinal cord parenchyma (arrows).

B, Parasagittal T2-weighted image (4000/102_eff /2) shows a large paracentral disk/osteophyte complex at the C3–C4 level (arrow).

C, Contrast-enhanced sagittal T1-weighted image (650/15/2) with fat saturation shows intense meningeal enhancement along the surface of the spinal cord. The patient was treated aggressively with broad-spectrum antibiotics and a decompressive laminectomy at C6 for a parasagittal epidural abscess (not shown).

D, Sagittal T1-weighted image (600/11/3) obtained 16 months later shows marked enlargement of the cervical spinal cord below the C3–C4 level. The parenchyma is hyperintense compared with CSF, and no evidence is detected of frank cavitation.

E, Sagittal T2-weighted image (4000/102/2) confirms the marked enlargement of the cervical cord below the C3–C4 level as well as extensive and confluent T2 prolongation within the central cord parenchyma. The cord surface is slightly irregular at C3–C4, suggesting possible adhesions.

F, Contrast-enhanced sagittal T1-weighted image (650/11/2) shows no abnormal enhancement of the cord parenchyma. Faint linear increased signal dorsal to the cord (arrows) likely represents residual thickening and fibrosis of the dura/epidural space related to the previous intense inflammatory episode.

G, Cervical CT myelogram was obtained several days later, via a lumbar approach. Axial image at the C7–T1 level shows normal-appearing spinal cord surrounded by dense intrathecal contrast.

H, Axial image from the CT myelogram at the C5–C6 level shows marked cord enlargement and minimal intrathecal contrast along the right lateral cord.

I, Axial image from the CT myelogram at the C3–C4 level shows a narrow spinal canal, a left lateral calcified disk/osteophyte complex, and a lack of contrast around the spinal cord.

J, Delayed CT scan obtained 6 hours after the initial study shows subtle increased density of the peripheral parenchyma at the C3–C4 level consistent with penetration of contrast medium. The central cord (arrow) stands out in subtle contrast to the more dense peripheral white matter.

K, Postoperative sagittal T2-weighted image (4000/102_eff /2) obtained after C3 to C7 laminectomy, lysis of subdural adhesions, and sectioning of the dentate ligaments at C3 and C4 shows a marked decrease in cord caliber. Parenchymal T2 prolongation persists, as does irregularity consistent with persistent adhesions/obstruction at the C3–C4 level. Because the patient was symptomatically improved, it was elected to monitor her with serial imaging studies rather than to reoperate.

A, Sagittal T1-weighted image (500/15/2) shows enlargement of the cervical cord and central parenchymal hypointensity. There is marked enlargement of the fourth ventricle and secondary tonsillar herniation with crowding of the foramen magnum.

B, Sagittal T2-weighted image (2500/102_eff /2) shows striking T2 prolongation within the central portion of the cord.

C, Axial T1-weighted image (583/17/2) at the C2–C3 level shows that the central cord hypointensity has an irregular margin and is not isointense with CSF.

D, Sagittal T1-weighted image (500/14/1.5) after treatment of hydrocephalus. The fourth ventricle is decompressed, the cerebellar tonsils are normally positioned, and cord caliber has returned to normal.

E, Sagittal T2-weighted image (2500/102_eff /2) shows complete resolution of previously noted parenchymal T2 prolongation. A dark line down the center of the cord (solid arrow) is presumably artifactual because of patient motion and/or truncation artifact, as other parallel lines (open arrow) are observed across the image.

A, Sagittal T2-weighted image (4000/108_eff /4) obtained when the patient had no symptoms referable to the spinal cord shows a mild dilatation of the obex/proximal central canal and central T2 prolongation within the upper cervical cord parenchyma.

B, Sagittal T1-weighted (left panel) (600/11/2) and T2-weighted (right panel) (3000/96_eff /2) images obtained 1 year later when the patient had developed progressive neck pain and spastic quadriparesis show striking cord expansion and both T1 and T2 prolongation within the cervical spinal cord. The areas of abnormal signal within the cord approach, but are not quite equal to, CSF in intensity.

C, Axial T1-weighted image (650/9/3) shows irregularly marginated central parenchymal hypointensity, although this area is hyperintense compared with CSF in the spinal canal. These images (A–C) were interpreted as consistent with syrinx by the neurosurgeon, and the patient was taken to the operating room for shunt placement. Intraoperatively, the cord was noted to be enlarged and "boggy." A myelotomy was performed at the C6 level, and a small amount of fluid exuded from the cord surface, but no syrinx was encountered. Intraoperative sonogram (not shown) confirmed the lack of frank cavitation.

D, Sagittal T2-weighted image (3500/96_eff /3) obtained 2 days postoperatively shows evidence of recent C6–C7 laminectomy. The cord is notably reduced in overall caliber compared with the preoperative study, and the signal has normalized at the myelotomy site (arrow).

E, Repeat T2-weighted image (2500/105_eff /3) obtained 8 days later shows further regression of signal abnormality and further reduction of cord caliber.

F, Sagittal T2-weighted image (3894/112_eff /1) obtained 1 month later shows an increase in central T2 prolongation within the cervical spinal cord, as well as an increase in cord caliber. The patient was doing fairly well in rehabilitation and did not desire further intervention. The patient was lost to follow-up for 10 months.

G, Sagittal T1-weighted image (500/8/3) obtained 11 months after surgery shows further enlargement of the cervical and upper thoracic spinal cord. The cord centrally is hypointense, and multiple septations are present (arrow) consistent with syringomyelia. The patient clinically was severely quadriparetic and had lost control of bowel and bladder function. After this image, surgery was performed, during which a large syrinx was encountered and a syringopleural shunt was placed (not shown).

A, Sagittal view of the craniocervical junction and upper cervical spinal cord in an anatomically normal patient shows no obstruction to CSF flow at the foramen magnum. A segment of spinal cord parenchyma (box) is shown in more detail in B.

B, Magnified view of the box in A shows CSF flow dynamics in a normal patient with a variably stenotic central canal (CC) (29), as indicated by the horizontal lines. CSF pressure (vertical arrow) is normal. CSF flows from the subarachnoid space (SAS) between the arachnoid (A) and pia (P) to the subpial space, and then enters the perivascular space (PVS). CSF circulates through the cord parenchyma toward the central canal, but may also flow in reverse, as these forces are relatively balanced under normal circumstances (double-headed arrows) (45, 46).

A, Sagittal view of the craniocervical junction in a patient with a Chiari I malformation shows abnormal descent of the cerebellar tonsil below the level of the foramen magnum (arrow). A segment of spinal cord parenchyma (box) is magnified in B to D, which represent views of CSF dynamics at the level of the spinal cord parenchyma in the presence of alterations in normal CSF flow and variable patency of the central canal.

B, Focal noncommunicating syrinx. In the setting of a Chiari I malformation and a variably stenotic central canal (which is a normal variant in many adults), as the tonsils descend rapidly during systole, CSF is driven into the spinal cord parenchyma by increased CSF pressure (thick vertical arrow). Net CSF flow occurs toward the central canal, resulting in focal syringomyelia, which is limited in its craniocaudal extent by intervening stenosis of the central canal. CC = central canal, A = arachnoid, P = pia, SAS = subarachnoid space, PVS = perivascular space.

C, Extensive noncommunicating syrinx. This situation is similar to B, but the central canal is more extensively patent. In this situation, a long-segment dilatation of the central canal occurs as CSF is driven into the central canal (curved arrows) via the perivascular spaces by the accentuated CSF pulse pressure (thick vertical arrow) that results from the downward motion of the low-lying cerebellar tonsils in systole.

D, "Presyrinx." In the setting of altered CSF flow, as with a Chiari I malformation, fluid in the subarachnoid space is subjected to increased pressure (thick vertical arrow). Net CSF flow is into the spinal cord parenchyma; however, because the central canal is not patent (as indicated by the horizontal lines), fluid cannot accumulate within the central canal (curved arrows) and, therefore, diffuses through the cord parenchyma (stippled area), resulting in cord enlargement and edema.