NelXoradiology
Intradiploic Neural Heterotopia A Rare Calvarial Defect 1 Kwang S. Kim, M.D., Lee F. Rogers, M.D., and Peter E. Weinberg, M.D. Two proved cases of intradiploic neural heterotopia of the skull, a rare cause of calvarial defects, are presented. The literature is reviewed. Common radiographic characteristics includean intradiploic rarefaction. a well-defined marginwith or without sclerosis, a lobulated appearance with normal intervening bone. or a cluster of multiple lytic areas with normal bone between them. INDEX TERMS: malities
(Calvarium, other misc. congenital anomaly, 1[1] .1499). Skull. abnor-
Radiology 125:425-427. November 1977
A N OSTEOLYTIC LESION of the skull caused by hetero1-\ topic neural tissue is a rare developmental anomaly. We have found only 2 cases reported in the English literature (1, 2). We wish to present 2 proved cases of this entity, review the literature, and discuss the common radiographic characteristics of this lesion.
T ABLE I: REFERENCE
1 4
CASE REPORTS CASE I: A 45-year-old woman was hospitalized because of a oneyear history of headaches which were nonspecific and variable in character . The physical and neurological examinations were unremarkable except for the detection of a soft. slightly tender depressed
RAD IOGRAPHIC FINDINGS IN PROVED CASES
LOCATION OF LESION RADIOGRAPHIC CHARA CTERISTICS
Occipital
A cluster of multiple lytic lesions with normal bone between them . Fairly well-circumscribed margins.
2
Occipital Occipital Parietal
A cluster of mult iple lytic lesions with normal bone . Fairly well-circumscribed margins. A lobulated lytic lesion with intervening normal bone in the midportion . Fairly well-circumscribed margin. A lobulated lytic les ion with central bony islands. Fairly well-circumscribed marg in.
Kimetal. Case I
Parietal
Case II
Frontal
A lobulated lytic lesion with intervening normal bone within. Well-circumscribed margin. Smooth erosion of the inner table from inside with an outwardly convex appearance on polytomogram . A lobulated lytic lesion with intervening normal bone within. Sclerotic margin.
Case I Case II
Fig. 1. Lateral view of skull showing a lobulated osteolytic lesion in the parietal region. The lytic area is interspersed with normal bone. Fig. 2. Tomographic tangential anteroposterior projection through the interveningbone (arrow) shows smooth erosion with outwardly convex appearance of the inner table, indicating that the lesion originates inside the skull.
1
From the Department of Radiology, Northwestern Memorial Hospital, Chicago, III. Accepted for publication in August. 1977.
425
ss
426
KWANG
S.
KIM AND OTHERS
.,
•
•
•• •
•
Fig', 3. A photomicrograph of the heterotopic neural tissue shows normal brain tissue with glial cells and neurons (H & E X 200).
area in the right parietal region of the skull. Routinelaboratory tests were normal. Plain skull images revealed a fairly well-circumscribed and lobulated osteolytic lesion in the right parietal region (Fig. 1). The lytic area was interspersed with normal bone. Polytomograms demonstrated a welldemarcated intradiploic rarefaction with marked thinning and almost complete absence of the inner and outer tables. Posteriorly, in the section through the intervening bone, the inner table was smoothly eroded from the inside, with an outwardly convex appearance (Fig. 2). This was thought to indicate that the process originated inside the skull. A computed tomogram of the head revealed normal brain , and a bone scan failed to show any abnormal uptake in the skull or elsewhere. At surgery, the outer table of the skull at the site of the lesion was found to be paper-thin but intact. It had a bluish discoloration. The lesion, located in the diploe, consisted of multiple lobulations of a smooth glistening and bluish tissue. A craniectomy was performed around the lesion. After the lesion had been removed, it was noted that several small perforations in the dura were present. Apparently some brain tissue had herniated through these perforations into the lesion . There
November 1977
were some dilated vessels in the dura mater which were cauterized. Microscopic examination of the surgical specimen showed normal cerebral tissue with glial cells and neurons (Fig. 3). Left hemiparesis developed following surgery. Computed tomography revealed an area of low density in the right parietal region, and a minimal shift of the midline structures to the left side. The area of abnormality was believed to represent infarction, probably created by cortical venous ttYombosis, following cauterization of the dural vessels at the time of surgery. The patient completely recovered during the subsequent two weeks and was discharged . CASE II: A 21-year-old woman was hospitalized because of recurrence of rhinorrhea and symptoms of hydrocephalus. The patient had had two previous craniectomies for spontaneous rhinorrhea and repeated episodes of meningitis. Skull images revealed a small lytic lesion in the right frontal region which was lobulated and well-circumscribed with a sclerotic margin. The lytic area was interspersed with bone of normal density (Fig. 4, A and B). Computed tomography of the head demonstrated the presence of hydrocephalus with no other abnormality. A bifrontal craniectomy was performed in order to repair the dural defects. The area of the lytic lesion in the right frontal region was incidentally included in the bone flap . The outer table of the skull at the site of the lesion was thinned, and within the diploic space was a lobulated mass of tissue which was reddish in color and rubbery in consistency. The inner table of the skull was absent and the underlyingdura was intact. Microscopic examination of the tissue revealed normal cerebral tissue with glial cells and neurons (Fig. 5).
DISCUSSION
Goldring et al. first reported a case of multiple osteolytic lesions of the suboccipital bone produced by neural tissue (1). The lesions were located in the intradiploic space and the underlying dura was intact. There was no connection with the brain. They termed this condition ectopic neural tissue of the occipital bone. Thompson submitted the skull images of two proved
Fig. 4. Lateral (A) and postero-anterior (B) views demonstrate a lobulated lytic area in the frontal bone with a well-circumscribed sclerotic margin and intervening normal bone.
427
INTRADIPLOIC NEURAL HETEROTOPIA
Vol. 125
cases with ectopic glial rests of the occipital bone to the American College of Radiology Learning Laboratory (4). One of these cases closely resembled that of Golding et al. in that a cluster of multiple lytic lesions was present in the occipital region. The other case showed a lobulated lytic lesion with normal intervening bone in the mid-portion. Kosnik et al. recently reported a case with an osteolytic lesion in the parietal bone caused by intradiploic herniation of cerebral tissue through a large dural defect in the form of an encephalocele (2). The osteolytic lesion was lobulated and fairly well-circumscribed, with central bony islands. Our CASE I is similar to the one reported by Kosnik et al. in that the lesion was located in the parietal region and there was a connection with the brain. The connection in this case consisted of perforations in the dura through which cerebral tissue herniated. forming a lobulated and cauliflower-like lesion in the diploe. In our CASE II. the underlying dura was intact. The lesions were asymptomatic in our 2 cases and in all prior cases. The radiographic findings of all the proved cases are summarized in TABLE I. Common radiographic characteristics include an intradiploic rarefaction, a circumscribed margin with or without sclerosis, a lobulated appearance with normal intervening bone within. or a cluster of multiple lytic areas with normal bone between them . The appearance of a smooth erosion of the inner table of the skull (Fig. 2), indicating a slow benign process originating inside the skull, may be an important differential point when present. The bone scan was normal in our CASE I. Although no information on bone scans was available in the other cases. this may also be important to the differential diagnosis. SUMMARY
The presence of an osteolytic defect, or a cluster of
•
.
•
~
•
Neuroradiology
-., .
•
... ,
••
•
•
•
•
• .'---~-
Fig. 5. A photomicrograph of the heterotopic neural tissue shows normal brain tissue with glial cells and neurons (H & E X 200).
defects. located in the diploic space of the skull, and having a circumscribed and lobulated margin with normal intervening bone, should strongly suggest the diagnosis of intradiploic neural heterotopia when the bone scan is normal. By utilizing these radiographic criteria. unnecessary surgery may be avoided. Department of Radiology Northwestern Memorial Hospital Superior St. and Fairbanks Court Chicago. III. 60611
REFERENCES
1. Goldring S, Hodges FH, Luse SA: Ectopic neural tissue of occipital bone. J Neurosurg 21:479-484, Jun 1964 2. Kosnik E, Meagher IN, Quenemoen LR: Parietal intradiploic encephalocele. J Neurosurg 44:617-619, May 1976 3. Lee CM, McLaurin RL: Heterotopic brain tissue as an Isolated embryonic rest. J Neurosurg 12:190-195, Mar 1955 4. Thompson RD: Personal communication
Intradiploic Neural Heterotopia A Rare Calvarial Defect 1 Kwang S. Kim, M.D., Lee F. Rogers, M.D., and Peter E. Weinberg, M.D. Two proved cases of intradiploic neural heterotopia of the skull, a rare cause of calvarial defects, are presented. The literature is reviewed. Common radiographic characteristics includean intradiploic rarefaction. a well-defined marginwith or without sclerosis, a lobulated appearance with normal intervening bone. or a cluster of multiple lytic areas with normal bone between them. INDEX TERMS: malities
(Calvarium, other misc. congenital anomaly, 1[1] .1499). Skull. abnor-
Radiology 125:425-427. November 1977
A N OSTEOLYTIC LESION of the skull caused by hetero1-\ topic neural tissue is a rare developmental anomaly. We have found only 2 cases reported in the English literature (1, 2). We wish to present 2 proved cases of this entity, review the literature, and discuss the common radiographic characteristics of this lesion.
T ABLE I: REFERENCE
1 4
CASE REPORTS CASE I: A 45-year-old woman was hospitalized because of a oneyear history of headaches which were nonspecific and variable in character . The physical and neurological examinations were unremarkable except for the detection of a soft. slightly tender depressed
RAD IOGRAPHIC FINDINGS IN PROVED CASES
LOCATION OF LESION RADIOGRAPHIC CHARA CTERISTICS
Occipital
A cluster of multiple lytic lesions with normal bone between them . Fairly well-circumscribed margins.
2
Occipital Occipital Parietal
A cluster of mult iple lytic lesions with normal bone . Fairly well-circumscribed margins. A lobulated lytic lesion with intervening normal bone in the midportion . Fairly well-circumscribed margin. A lobulated lytic les ion with central bony islands. Fairly well-circumscribed marg in.
Kimetal. Case I
Parietal
Case II
Frontal
A lobulated lytic lesion with intervening normal bone within. Well-circumscribed margin. Smooth erosion of the inner table from inside with an outwardly convex appearance on polytomogram . A lobulated lytic lesion with intervening normal bone within. Sclerotic margin.
Case I Case II
Fig. 1. Lateral view of skull showing a lobulated osteolytic lesion in the parietal region. The lytic area is interspersed with normal bone. Fig. 2. Tomographic tangential anteroposterior projection through the interveningbone (arrow) shows smooth erosion with outwardly convex appearance of the inner table, indicating that the lesion originates inside the skull.
1
From the Department of Radiology, Northwestern Memorial Hospital, Chicago, III. Accepted for publication in August. 1977.
425
ss
426
KWANG
S.
KIM AND OTHERS
.,
•
•
•• •
•
Fig', 3. A photomicrograph of the heterotopic neural tissue shows normal brain tissue with glial cells and neurons (H & E X 200).
area in the right parietal region of the skull. Routinelaboratory tests were normal. Plain skull images revealed a fairly well-circumscribed and lobulated osteolytic lesion in the right parietal region (Fig. 1). The lytic area was interspersed with normal bone. Polytomograms demonstrated a welldemarcated intradiploic rarefaction with marked thinning and almost complete absence of the inner and outer tables. Posteriorly, in the section through the intervening bone, the inner table was smoothly eroded from the inside, with an outwardly convex appearance (Fig. 2). This was thought to indicate that the process originated inside the skull. A computed tomogram of the head revealed normal brain , and a bone scan failed to show any abnormal uptake in the skull or elsewhere. At surgery, the outer table of the skull at the site of the lesion was found to be paper-thin but intact. It had a bluish discoloration. The lesion, located in the diploe, consisted of multiple lobulations of a smooth glistening and bluish tissue. A craniectomy was performed around the lesion. After the lesion had been removed, it was noted that several small perforations in the dura were present. Apparently some brain tissue had herniated through these perforations into the lesion . There
November 1977
were some dilated vessels in the dura mater which were cauterized. Microscopic examination of the surgical specimen showed normal cerebral tissue with glial cells and neurons (Fig. 3). Left hemiparesis developed following surgery. Computed tomography revealed an area of low density in the right parietal region, and a minimal shift of the midline structures to the left side. The area of abnormality was believed to represent infarction, probably created by cortical venous ttYombosis, following cauterization of the dural vessels at the time of surgery. The patient completely recovered during the subsequent two weeks and was discharged . CASE II: A 21-year-old woman was hospitalized because of recurrence of rhinorrhea and symptoms of hydrocephalus. The patient had had two previous craniectomies for spontaneous rhinorrhea and repeated episodes of meningitis. Skull images revealed a small lytic lesion in the right frontal region which was lobulated and well-circumscribed with a sclerotic margin. The lytic area was interspersed with bone of normal density (Fig. 4, A and B). Computed tomography of the head demonstrated the presence of hydrocephalus with no other abnormality. A bifrontal craniectomy was performed in order to repair the dural defects. The area of the lytic lesion in the right frontal region was incidentally included in the bone flap . The outer table of the skull at the site of the lesion was thinned, and within the diploic space was a lobulated mass of tissue which was reddish in color and rubbery in consistency. The inner table of the skull was absent and the underlyingdura was intact. Microscopic examination of the tissue revealed normal cerebral tissue with glial cells and neurons (Fig. 5).
DISCUSSION
Goldring et al. first reported a case of multiple osteolytic lesions of the suboccipital bone produced by neural tissue (1). The lesions were located in the intradiploic space and the underlying dura was intact. There was no connection with the brain. They termed this condition ectopic neural tissue of the occipital bone. Thompson submitted the skull images of two proved
Fig. 4. Lateral (A) and postero-anterior (B) views demonstrate a lobulated lytic area in the frontal bone with a well-circumscribed sclerotic margin and intervening normal bone.
427
INTRADIPLOIC NEURAL HETEROTOPIA
Vol. 125
cases with ectopic glial rests of the occipital bone to the American College of Radiology Learning Laboratory (4). One of these cases closely resembled that of Golding et al. in that a cluster of multiple lytic lesions was present in the occipital region. The other case showed a lobulated lytic lesion with normal intervening bone in the mid-portion. Kosnik et al. recently reported a case with an osteolytic lesion in the parietal bone caused by intradiploic herniation of cerebral tissue through a large dural defect in the form of an encephalocele (2). The osteolytic lesion was lobulated and fairly well-circumscribed, with central bony islands. Our CASE I is similar to the one reported by Kosnik et al. in that the lesion was located in the parietal region and there was a connection with the brain. The connection in this case consisted of perforations in the dura through which cerebral tissue herniated. forming a lobulated and cauliflower-like lesion in the diploe. In our CASE II. the underlying dura was intact. The lesions were asymptomatic in our 2 cases and in all prior cases. The radiographic findings of all the proved cases are summarized in TABLE I. Common radiographic characteristics include an intradiploic rarefaction, a circumscribed margin with or without sclerosis, a lobulated appearance with normal intervening bone within. or a cluster of multiple lytic areas with normal bone between them . The appearance of a smooth erosion of the inner table of the skull (Fig. 2), indicating a slow benign process originating inside the skull, may be an important differential point when present. The bone scan was normal in our CASE I. Although no information on bone scans was available in the other cases. this may also be important to the differential diagnosis. SUMMARY
The presence of an osteolytic defect, or a cluster of
•
.
•
~
•
Neuroradiology
-., .
•
... ,
••
•
•
•
•
• .'---~-
Fig. 5. A photomicrograph of the heterotopic neural tissue shows normal brain tissue with glial cells and neurons (H & E X 200).
defects. located in the diploic space of the skull, and having a circumscribed and lobulated margin with normal intervening bone, should strongly suggest the diagnosis of intradiploic neural heterotopia when the bone scan is normal. By utilizing these radiographic criteria. unnecessary surgery may be avoided. Department of Radiology Northwestern Memorial Hospital Superior St. and Fairbanks Court Chicago. III. 60611
REFERENCES
1. Goldring S, Hodges FH, Luse SA: Ectopic neural tissue of occipital bone. J Neurosurg 21:479-484, Jun 1964 2. Kosnik E, Meagher IN, Quenemoen LR: Parietal intradiploic encephalocele. J Neurosurg 44:617-619, May 1976 3. Lee CM, McLaurin RL: Heterotopic brain tissue as an Isolated embryonic rest. J Neurosurg 12:190-195, Mar 1955 4. Thompson RD: Personal communication
