Neuroradiology
Kinking of the Aqueduct of Sylvius in the Absence of Posterior Fossa Masses 1 David P. Winestock, M.D. The kinked or "hockey stick" deformity of the aqueduct of Sylvius has long been considered pathognomonic of a mass in the posterior fossa. Five patients with kinking of the aqueduct of Sylvius are described. All had intracranial abnormalities but none had a mass in the posterior fossa. INDEX TERMS:
Aqueduct of Sylvius • Posterior Fossa • Skull, pressure in
Radiology 116:345-348, August 1975
first described by Lysholm in 1935 (4), the kinked aqueduct of Sylvius has been considered pathognomonic of space-occupying lesions of the posterior fossa. Three years later, Hyndman (2) reported 4 cases of tumor in or pressing on the cerebellar vermis, causing a kinked aqueduct. He concluded that "a consistent angular deformity of the aqueduct of Sylvius provides ventriculographic evidence of a tumor in or compressing the cerebellar vermis." The following year (1939) Lysholm (5) and Twining (9) independently demonstrated that any mass of the posterior fossa located posteriorly or posterolaterally to the fourth ventricle could angulate the aqueduct. Since that time, both scientific articles (1, 6) and textbooks (7, 8) have reinforced the premise that a kinked aqueduct means that a posterior fossa mass is present. Lindgren and Oi Chiro (3) were the first to suggest that a kinked aqueduct could be a variation of the normal. The two examples reproduced in their publication, however, show only minimal kinking. The following cases will demonstrate that the aqueduct of Sylvius can be moderately to severely kinked in patients who have intracranial abnormalities but no space-occupying lesions in the posterior fossa.
S
INCE
CASE REPORTS CASE I. A 61-year-old man was admitted to the hospital for observation after a skull fracture. The neurologic examination revealed truncal ataxia and mild dementia. A radionuclide cisternagram showed normal findings except for delayed flow of nuclide over the cerebral hemispheres. On the early films of the pneumoencephalogram, a kink of the cerebral aqueduct was noted (Fig. 1, A). The size of the pontine cistern was normal or slightly enlarged, indicating that the brainstem had not been displaced anteriorly (Fig. 1, B). The lateral ventricles were also enlarged (Fig. 1, C). A subsequent angiogram
of the posterior fossa confirmed the absence of a space-occupying lesion (Fig. 1, D). The final diagnosis was cerebral atrophy. CASE II. A four-month-old boy was admitted to the hospital for evaluation of a meningomyelocele and an enlarging head. To investigate the increasing circumference of his head, a pneumoencephalogram was obtained. In addition to moderately dilated fourth, third, and lateral ventricles, a severe kink of the aqueduct was seen (Fig. 2). The fourth ventricle was displaced below the level of the foramen magnum, allowing the diagnosis of Arnold-Chiari malformation. The child succumbed to repeated episodes of meningitis. At necropsy, no mass could be found in the posterior fossa. CASE III. A 16-year-old boy complained of headaches, double vision, nausea, and vomiting. Examination revealed bilateral papilledma and paresis of upward gaze. A large, calcified pineal body was identified on the skull radiograph, and on the pneumoencephalogram a kink in the aqueduct was noted (Fig. 3). The normal position of Twining's point (constructed in Fig. 3) indicated that the fourth ventricle was not displaced which therefore excluded a mass in the posterior fossa. The clinical diagnosis was pinealoma. CASE IV. While hospitalized for an unrelated problem, a 70-yearold man was found to have the clinical triad of dementia, gait disability, and urinary incontinence. Normal pressure hydrocephalus was strongly suspected after a radionuclide cisternagram demonstrated entrance of the nuclide into the ventricles with no flow over the cerebral convexities. At pneumoencephalography, a kinked aqueduct was noted but there was no displacement of the fourth ventricle, as indicated by the position of Twining's point (Fig. 4, A). The lateral ventricles were grossly enlarged (Fig. 4, B). The diagnosis was normal pressure hydrocephalus. CASE V. An 8-year-old girl had a two-month history of headache, double vision, nausea, and vomiting. A cerebral angiogram indicated a mass in the left thalamic region. Pneumoencephalography demonstrated a thalamic mass extending into the posterior aspect of the third ventricle and a marked kink in the aqueduct (Fig. 5). The position of Twining's point was normal. The diagnosis of thalamic as-
1 From the Departments of Radiology, University of California School of Medicine and San Francisco General Hospital, San Francisco, Calif. Accepted for publication in November 1974. shan
345
346
DAVID
P.
WINESTOCK
August 1975
Fig. 1. CASE I. A. Kinked aqueduct of Sylvius in a patient with cerebral atrophy. B. Pneumoencephalogram, brow-up position. The prepontine cistern is normal or slightly enlarged as indicated by the distance between the clivus (arrowheads) and the pons (arrows). C. Dilatation of the lateral ventricles, including the temporal horns. D. Tomogram of arterial phase of the lett vertebral angiogram . The choroidal point of the posterior inferior cerebellar artery (large black arrow) is seen in its normal pos ition. The basilar artery (white arrows) is at a normal distance from the clivus (small arrows).
trocytoma with extension into the third ventricle was confirmed surgically.
DISCUSSION
It is clearly impossible to define exactly the mechanical processes responsible for the kinking of the aqueduct. The complexity of the brain structure defies the application of basic principles of vector force. However,
in 2 of our cases (the pinealoma and the thalamic astrocytoma), it might be postulated simply that the tumor mass displaced the cephalad portion of the aqueduct inferiorly. The kinking seen in the other 3 cases is more difficult to understand: perhaps the large lateral ventricles were responsible for the caudad displacement of the midbrain. More important than understanding the mechanical
Vol. 116
KINKING OF THE AQUEDUCT OF SVLVIUS
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Neuroradiology
Fig . 2. CASE II. Severely kinked aqueduct in a pat ient with Arnold-Chiari malformation. The inferior aspect of the fourth ventricle extends below the foramen magnum. Fig. 3. CASE III. Angulated aqueduct in a patient with pinealoma. TWining's point, indicated by the intersection of the perpendicular lines (-l), is in the normal position.
cause of the kinking is the recognition that a kinked aqueduct can indicate the presence of a supratentorial intracranial abnormality. In conclusion, the kinked aqueduct of Sylvius is not pathognomonic of a mass of the posterior fossa. In-
deed, Lindgren and Oi Chiro (3) reported that minimal kinking may be found in normal patients. It is now evident that kinking can also occur in patients with intracranial abnormalities other than posterior fossa masses .
Fig. 4. CASE IV. A . Kinked aqueduct in a pat ient with normal pressure hydrocephalus. The normal position of Twining's point (arrowhead) indicates that the fourth ventricle is not displaced. B. Skull radiograph. The anterior horns of the laterai ventricles are enlarged.
348
DAVID
P.
WINESTOCK
August 1975
REFERENCES 1. Hilal SK, Tookoian H, Wood EH: Displacement of the aqueduct of Sylvius by posterior fossa tumors. Exper imental and clinical studies. Acta Radiol [Diagn] 9:167-182, 1969 2. Hyndman OR: Cerebral pneumography-ventriculographic interpretation of tumors in and about third ventricle, aqueduct of Sylvius and fourth ventricle. Arch Surg 36:245-291, Feb 1938 3. Lindgren E, Di Chiro G: The roentgenologic appearance of the aqueduct of Sylvius. Acta RadioI39:117-125, Feb 1953 4. Lysholm E: Das Ventrikulogramm. Part III: Dritter und vierter Ventrikel. Acta Radiol (SuppI26):65-79, 1935 5. Lysholm E: Ventriculography of the fourth ventricle. Am J RoentgenoI41:18-24, Jan 1939 6. Lysholm E: Experiences in ventriculography of tumours below the tentorium. Br J RadioI19:437-452, Nov 1946 7. Robertson EG: Pneumoencephalography. Springfield, III., Thomas, 1957, pp 153-154 8. Taveras JM, Wood EH: Diagnostic Neuroradiology. Baltimore , Williams & Wilkins, 1964, pp 1.421-1.422 9. Twining EW: Radiology of the third and fourth ventricles. Part II. Br J RadioI12:569-598, Oct 1939
Fig. 5. CASE V. Aqueduct of Sylvius showing marked kinking. A thalamic mass is seen extending into the posterior aspect of the third ventricle (arrowheads). The position of Twining's point ( ..l) is normal.
David P. Winestock, M.D. Department of Radiology, M-380 University of California San Francisco, Calif . 94143
Kinking of the Aqueduct of Sylvius in the Absence of Posterior Fossa Masses 1 David P. Winestock, M.D. The kinked or "hockey stick" deformity of the aqueduct of Sylvius has long been considered pathognomonic of a mass in the posterior fossa. Five patients with kinking of the aqueduct of Sylvius are described. All had intracranial abnormalities but none had a mass in the posterior fossa. INDEX TERMS:
Aqueduct of Sylvius • Posterior Fossa • Skull, pressure in
Radiology 116:345-348, August 1975
first described by Lysholm in 1935 (4), the kinked aqueduct of Sylvius has been considered pathognomonic of space-occupying lesions of the posterior fossa. Three years later, Hyndman (2) reported 4 cases of tumor in or pressing on the cerebellar vermis, causing a kinked aqueduct. He concluded that "a consistent angular deformity of the aqueduct of Sylvius provides ventriculographic evidence of a tumor in or compressing the cerebellar vermis." The following year (1939) Lysholm (5) and Twining (9) independently demonstrated that any mass of the posterior fossa located posteriorly or posterolaterally to the fourth ventricle could angulate the aqueduct. Since that time, both scientific articles (1, 6) and textbooks (7, 8) have reinforced the premise that a kinked aqueduct means that a posterior fossa mass is present. Lindgren and Oi Chiro (3) were the first to suggest that a kinked aqueduct could be a variation of the normal. The two examples reproduced in their publication, however, show only minimal kinking. The following cases will demonstrate that the aqueduct of Sylvius can be moderately to severely kinked in patients who have intracranial abnormalities but no space-occupying lesions in the posterior fossa.
S
INCE
CASE REPORTS CASE I. A 61-year-old man was admitted to the hospital for observation after a skull fracture. The neurologic examination revealed truncal ataxia and mild dementia. A radionuclide cisternagram showed normal findings except for delayed flow of nuclide over the cerebral hemispheres. On the early films of the pneumoencephalogram, a kink of the cerebral aqueduct was noted (Fig. 1, A). The size of the pontine cistern was normal or slightly enlarged, indicating that the brainstem had not been displaced anteriorly (Fig. 1, B). The lateral ventricles were also enlarged (Fig. 1, C). A subsequent angiogram
of the posterior fossa confirmed the absence of a space-occupying lesion (Fig. 1, D). The final diagnosis was cerebral atrophy. CASE II. A four-month-old boy was admitted to the hospital for evaluation of a meningomyelocele and an enlarging head. To investigate the increasing circumference of his head, a pneumoencephalogram was obtained. In addition to moderately dilated fourth, third, and lateral ventricles, a severe kink of the aqueduct was seen (Fig. 2). The fourth ventricle was displaced below the level of the foramen magnum, allowing the diagnosis of Arnold-Chiari malformation. The child succumbed to repeated episodes of meningitis. At necropsy, no mass could be found in the posterior fossa. CASE III. A 16-year-old boy complained of headaches, double vision, nausea, and vomiting. Examination revealed bilateral papilledma and paresis of upward gaze. A large, calcified pineal body was identified on the skull radiograph, and on the pneumoencephalogram a kink in the aqueduct was noted (Fig. 3). The normal position of Twining's point (constructed in Fig. 3) indicated that the fourth ventricle was not displaced which therefore excluded a mass in the posterior fossa. The clinical diagnosis was pinealoma. CASE IV. While hospitalized for an unrelated problem, a 70-yearold man was found to have the clinical triad of dementia, gait disability, and urinary incontinence. Normal pressure hydrocephalus was strongly suspected after a radionuclide cisternagram demonstrated entrance of the nuclide into the ventricles with no flow over the cerebral convexities. At pneumoencephalography, a kinked aqueduct was noted but there was no displacement of the fourth ventricle, as indicated by the position of Twining's point (Fig. 4, A). The lateral ventricles were grossly enlarged (Fig. 4, B). The diagnosis was normal pressure hydrocephalus. CASE V. An 8-year-old girl had a two-month history of headache, double vision, nausea, and vomiting. A cerebral angiogram indicated a mass in the left thalamic region. Pneumoencephalography demonstrated a thalamic mass extending into the posterior aspect of the third ventricle and a marked kink in the aqueduct (Fig. 5). The position of Twining's point was normal. The diagnosis of thalamic as-
1 From the Departments of Radiology, University of California School of Medicine and San Francisco General Hospital, San Francisco, Calif. Accepted for publication in November 1974. shan
345
346
DAVID
P.
WINESTOCK
August 1975
Fig. 1. CASE I. A. Kinked aqueduct of Sylvius in a patient with cerebral atrophy. B. Pneumoencephalogram, brow-up position. The prepontine cistern is normal or slightly enlarged as indicated by the distance between the clivus (arrowheads) and the pons (arrows). C. Dilatation of the lateral ventricles, including the temporal horns. D. Tomogram of arterial phase of the lett vertebral angiogram . The choroidal point of the posterior inferior cerebellar artery (large black arrow) is seen in its normal pos ition. The basilar artery (white arrows) is at a normal distance from the clivus (small arrows).
trocytoma with extension into the third ventricle was confirmed surgically.
DISCUSSION
It is clearly impossible to define exactly the mechanical processes responsible for the kinking of the aqueduct. The complexity of the brain structure defies the application of basic principles of vector force. However,
in 2 of our cases (the pinealoma and the thalamic astrocytoma), it might be postulated simply that the tumor mass displaced the cephalad portion of the aqueduct inferiorly. The kinking seen in the other 3 cases is more difficult to understand: perhaps the large lateral ventricles were responsible for the caudad displacement of the midbrain. More important than understanding the mechanical
Vol. 116
KINKING OF THE AQUEDUCT OF SVLVIUS
347
Neuroradiology
Fig . 2. CASE II. Severely kinked aqueduct in a pat ient with Arnold-Chiari malformation. The inferior aspect of the fourth ventricle extends below the foramen magnum. Fig. 3. CASE III. Angulated aqueduct in a patient with pinealoma. TWining's point, indicated by the intersection of the perpendicular lines (-l), is in the normal position.
cause of the kinking is the recognition that a kinked aqueduct can indicate the presence of a supratentorial intracranial abnormality. In conclusion, the kinked aqueduct of Sylvius is not pathognomonic of a mass of the posterior fossa. In-
deed, Lindgren and Oi Chiro (3) reported that minimal kinking may be found in normal patients. It is now evident that kinking can also occur in patients with intracranial abnormalities other than posterior fossa masses .
Fig. 4. CASE IV. A . Kinked aqueduct in a pat ient with normal pressure hydrocephalus. The normal position of Twining's point (arrowhead) indicates that the fourth ventricle is not displaced. B. Skull radiograph. The anterior horns of the laterai ventricles are enlarged.
348
DAVID
P.
WINESTOCK
August 1975
REFERENCES 1. Hilal SK, Tookoian H, Wood EH: Displacement of the aqueduct of Sylvius by posterior fossa tumors. Exper imental and clinical studies. Acta Radiol [Diagn] 9:167-182, 1969 2. Hyndman OR: Cerebral pneumography-ventriculographic interpretation of tumors in and about third ventricle, aqueduct of Sylvius and fourth ventricle. Arch Surg 36:245-291, Feb 1938 3. Lindgren E, Di Chiro G: The roentgenologic appearance of the aqueduct of Sylvius. Acta RadioI39:117-125, Feb 1953 4. Lysholm E: Das Ventrikulogramm. Part III: Dritter und vierter Ventrikel. Acta Radiol (SuppI26):65-79, 1935 5. Lysholm E: Ventriculography of the fourth ventricle. Am J RoentgenoI41:18-24, Jan 1939 6. Lysholm E: Experiences in ventriculography of tumours below the tentorium. Br J RadioI19:437-452, Nov 1946 7. Robertson EG: Pneumoencephalography. Springfield, III., Thomas, 1957, pp 153-154 8. Taveras JM, Wood EH: Diagnostic Neuroradiology. Baltimore , Williams & Wilkins, 1964, pp 1.421-1.422 9. Twining EW: Radiology of the third and fourth ventricles. Part II. Br J RadioI12:569-598, Oct 1939
Fig. 5. CASE V. Aqueduct of Sylvius showing marked kinking. A thalamic mass is seen extending into the posterior aspect of the third ventricle (arrowheads). The position of Twining's point ( ..l) is normal.
David P. Winestock, M.D. Department of Radiology, M-380 University of California San Francisco, Calif . 94143
