Neurosurgical procedures in Olmsted County, Minnesota, 1970-1974 Neurosurgical needs of a community GLEN G. GLISTA,M.D., R o s s H. MILLER, M.D.,
LEONARD T. KURLAND, M . D . , AND MARK L. JERECZEK
Mayo Clinic and Mayo Foundation, Rochester, Minnesota ~" To help determine neurosurgical needs within communities and within the nation, operations and diagnostic procedures performed by neurosurgeons on residents of Olmsted County, Minnesota, in the 5 years of 1970 through 1974, were tabulated. This county was studied because its medical records are virtually complete. Annual rates (per 100,000 population) were 42 for lumbar disc removal, six for cervical disc removal, and seven for brain-tumor therapy. Other less frequent occasions for neurological surgery are also tabulated. KEY WORDS epidemiology
9 neurosurgical m a n p o w e r 9 cerebral angiography 9 9 brain neoplasms 9 intervertebral disc displacement
HE existing number and the optimal number of neurosurgeons in the United States have been subjects of discussion among neurosurgeons and various governmental agencies for many y e a r s ) ,7 It has been estimated that in the United States there is one neurological surgeon per 100,000 population, but most of these specialists are in urban communities, particularly in the largest cities, and in academic and referral centers. Difficulties in determining an ideal number and pattern of distribution among the population include the uncertainty as to the number and variety o f diagnostic and surgical activities a neurological surgeon can be expected to p e r f o r m for a hypothetical average community of 100,000 people. We are reporting the number and type of procedures performed by neurosurgeons in a circumscribed population (Olmsted County,
T
46
Minnesota), over a 5-year period. We hope that this account will help to determine the neurosurgical needs of a community and provide young neurosurgeons with some idea of what procedures they may be called on to perform. S o u r c e o f Information
It is recognized that no single community can be considered as representative of the United States, since incidence rates, particularly for trauma, m a y vary widely with age, sex, race, automobile commuting practices, and industrial hazards. The experience in Olmsted County, Minnesota, provides incidence rates for many neurological and neurosurgical disorders in a defined community? The advantages of using the neurosurgical experience available in this area J. Neurosurg. / Volume 46 / January, 1977
Community needs for neurosurgery appear to outweigh the possible limitations with regard to its size, location, and population composition. Many of the estimates of incidence and prevalence of neurological diseases in the United States have come from previous studies of this community. 1,2,',6,8 The Mayo Clinic in Rochester has served for several decades as essentially the only source of medical care for this population. This unique medical record system, maintained for more than 40 years, readily identifies all medical encounters and diagnoses of local residents at the Mayo Clinic offices, affiliated hospitals (including emergency rooms), and home visits. In 70% of deaths among the local population, autopsy is performed by the Mayo Clinic Department of Pathology and Anatomy. The record-indexing system currently includes cases seen by the independent Olmsted Medical Group and other hospitals in and around Olmsted County. Since it is unlikely that any significant number of patients go elsewhere for diagnosis of serious illness or for any major surgery, the central data file maintained at the Mayo Clinic contains records of virtually all health care in the county population. Neurosurgical practice for the Olmsted County population is conducted almost exclusively at the Mayo Clinic facilities, since all neurosurgeons within 50 miles of Rochester are at the Clinic. There are currently seven staff neurosurgeons and 21 neurosurgical residents at the Mayo Clinic and its affiliated hospitals. Although each consultant may be expected to provide any neurosurgical service, there has been an increasing tendency in recent years toward subspecialization, particularly for pediatric and vascular surgery. The breadth of experience and variety of specialty interests represented by this staff preclude referrals elsewhere for care. The generally conservative group practice and ease of consultation with members of the Neurology Department and other specialists limit neurosurgical intervention to those cases most likely to respond to such procedures. Materials and Methods
Our study was based on the records of all neurosurgical diagnostic procedures and operations performed at the Mayo Clinic from 1970 through 1974 on patients who were J. Neurosurg. / Volume 46 / January, 1977
residents of Olmsted County, Minnesota, at the time. It should be recognized that the relatively small numbers of some procedures performed during this period make it difficult to produce rates that can be applied without substantial allowance for chance fluctuation. Although we considered extending the length of the study to 10 years to provide larger and presumably more stable rates, recent changes in neurosurgical practice dictated that the most recent 5 years of experience would best serve the purposes of this investigation. The estimated population of Olmsted County, Minnesota, at the midpoint of this study, July 1, 1972, was 87,955. The numbers given below can be converted to the frequency per 100,000 by multiplying the average number per year by the factor 1.14. The population studied is comparatively well educated, almost entirely Caucasian, and slightly younger than the United States population as a whole. The major occupational centers in Rochester are the Mayo Clinic, affiliated hospitals, and a large IBM assembly plant and research center. There is little that could be considered as heavy industry. Just outside Rochester there is suburban housing, but the rest of the county is rural and largely concerned with farming. This study includes only those patients upon whom a neurosurgeon performed a diagnostic procedure or neurosurgical operation. It does not include patients who consulted a neurosurgeon for evaluation only or who received nonsurgical treatment only, such as conservative treatment for a lumbar disc or observation of a closed head injury. Most patients who have a diagnostic procedure or operation performed by a neurosurgeon are first evaluated by a neurologist at the Mayo Clinic. In addition to all intracranial surgery, the neurosurgical department at the Mayo Clinic performs all carotid endarterectomies and all vertebral disc surgery. Some operations for trauma of the peripheral nerves are performed in cooperation with orthopedic surgeons, especially when associated with orthopedic injury to an extrem. ity. Release of the transverse carpal ligament for median nerve compression at the wrist (carpal tunnel syndrome) is performed on occasion by neurosurgeons but more often by the orthopedic surgeons who may be concerned with other problems involving the wrist joint of the same patient. Sympathetic ,t7
G. G. Glista, et al. TABLE t
TABLE 2
Number of Olmsted County residents on whom neurosurgeons performed diagnostic procedures or operations*
Number of diagnostic procedures performed by neurosurgeons on Olmsted County residents
Procedure
1970
1971
1972
1973
1974
elective emergency total
119 24 143
128 19 147
111 18 129
121 14 135
107 9 116
Procedure angiography* carotid retrograde brachial pneumoencephalography ventriculography subdural tap total
*Diagnostic procedures included cerebral angiography, pneumoencephalography, ventriculography, a n d subdural taps.
1970
1971
1972
1973
1974
68 44
65 40
57 40
56 42
57 43
24
25
17
14
14
11 4 1 84
17 2 1 85
10 2 0 69
5 4 0 65
3 2 2 64
*The numbers listed for angiography are n u m b e r of vessels studied, often more than one in a patient.
ganglionectomy is also performed by general surgeons, particularly when peripheral vascular reconstructive procedures are indicated. Likewise, some peripheral nerve biopsies and temporal artery biopsies are performed by members of other departments at the Mayo Clinic. Only when the above procedures were performed by a neurosurgeon were they included in this report.
Summary of Findings The number of Olmsted County residents who underwent neurosurgical diagnostic procedures and operations performed by neurosurgeons during the years 1970 through 1974 is given in Table 1, the number of diag-
TABLE 3
Major cranial procedures performed on Olmsted County residents* Lesion or Procedure tumors supratentorial glioma meningioma pituitary t u m o r craniopharyngioma ectopic pinealoma infratentorial acoustic neurinoma metastatic lesion glioma medulloblastoma rhizotomy or compression for trigeminal neuralgia brain abscess aneurysm arteriovenous malformation carotid endarterectomy elevation of depressed fracture acrylic cranioplasty hematoma intracerebral subdural acute chronic (burr-hole evacuation) m e m b r a n e (removal by craniotomy) shunt cerebrospinal fluid subdural-peritoneal
1970
1971
1972
3
12
4
3
3 2 1 1 1
3 1
1973
1974
(8)t
4
9 (6)t
1
11
1
1 1
2 1 1 1 2 1 2 2
3 2 1 2 1 3 3
2
1
3 (2) 1 7 (4)
1 1
5 (4) 2 (1)
7 (5) 2
6 (5)
1
5 (4) 1
5
2 (1) 2
3 5
3 3
1
1
2
I
1
1 2
3 (2) 2
5 (4)
8 (6)
2 (1) 9 (6) 1
7 (5)
*The n u m b e r of patients, if different from the n u m b e r of procedures, is given in parentheses. t O n e patient with glioma had three operations. 48
J. Neurosurg. / Volume 46 / January, 1977
C o m m u n i t y needs for neurosurgery nostic procedures performed in Table 2, and the number of major cranial operations in Table 3. The following other major cranial procedures were performed only once (or in only one patient) during the 5-year period: stereotaxic cingulectomy; craniectomy for osteomyelitis of the skull; operations for arachnoid cyst, p o r e n c e p h a l i c cyst, and craniosynostosis; stereotaxic hypophysect o m y for diabetic r e t i n o p a t h y ; transsphenoidal hypophysectomy for carcinoma of the prostate; treatment for acute epidural hematoma; repair of traumatic mastoid cerebrospinal fluid leak (twice in one patient); and stereotaxic t h a l a m o t o m y (twice in one patient). T h e n u m b e r o f vertebral neurosurgical procedures is listed in Table 4. Other vertebral procedures performed only once in 5 years included meningomyelocele repair, excision of lumbar dermal sinus with intradural exploration, and biopsy of vertebral body. The number of operations by neurosurgeons for peripheral nerve trauma and various miscellaneous procedures is given in Table 5. Other minor procedures performed infrequently in 5 years included insertion of Crutchfield tongs (6), excision of sebaceous scalp cyst (3), skull biopsy (2), closed reduction C4-5 fracture (1), excision of dermal sinus of scalp (1), and excision of traumatic arteriovenous fistula of scalp (1). Removal of lumbar discs was performed at only one level in most cases. A few of the patients in 1972, 1973, and 1974 chose chemonucleolysis of the lumbar disc rather than an open operation. All patients who had chemonucleolysis were candidates for an open procedure and were offered chemonucleolysis as an option during a clinical trial. As explained, since all cervical and lumbar disc surgery at the M a y o Clinic is performed by the Department of Neurosurgery, the numbers reported probably reflect accurately the incidence of surgically treated disc disease in residents of Olmsted County.
Discussion
Table 2 shows t h a t the n u m b e r of .pneumoencephalograms performed declined in 1973 and 1974. This decline is most probably explained by introduction of the computerized t o m o g r a p h y (CT) scanner at this clinic in July, 1973. Patients with such J. Neurosurg. / Volume 46 / January, 1977
TABLE 4 Vertebral procedures performed by neurosurgeons on Olmsted County residents
Lesion or Procedure
1970 1971 1972 1973 1974
lumbar disc removal 38 with fusion 12 decompression for spondylosis 0 cervical disc removal 2 decompression for spondylosis 1 spinal cord tumor primary 0 metastatic 1 spinal exploration for trauma 2
37 14
35 9
42 1
33 4
0
1
0
0
6
9
5
4
1
0
2
4
0 0
0 0
1 1
0 1
4
2
1
0
problems as presenile dementia or seizures, who previously might have u n d e r g o n e pneumoencephalography, are being scanned by CT which demonstrates the ventricular system well. TABLE 5 Peripheral nerve surgery and other miscellaneous procedures performed by neurosurgeons on Olmsted County residents*
Lesion or Procedure temporal artery biopsy tracheostomy percutaneous cordotomy ulnar nerve translocation median nerve decompression for carpal tunnel syndrome sympathectomy peripheral nerve tumor radiofrequency lesion of Gasserian ganglion brachial plexus exploration exploration or repair of peripheral nerves
1970 1971 1972 1973 1974 2 3
8 1
1 4
7 1
8
12
3
3 (2) 2
1 1
1
2 (1)
1
5 (3)
1
If
1
1
2
2
1 7
1
1
*The number of patients, if different from number of procedures, is given in parentheses. tNeurofibroma in flank. 49
G. G. Glista, e t al. TABLE 6 Annual frequency per 100,000 population of some selected operations
Operation
Frequency per 100,000
cerebral angiography brain tumor aneurysm arteriovenous malformations carotid endarterectomy lumbar disc removal cervical disc removal ulnar nerve translocation elevation of depressed fracture evacuation of intracerebral hematoma
66.8 7.1 4.3 0.9 2.5 42.2 5.9 2.3 3.4 1.1
Most frequent among the emergency procedures carried out was cerebral angiography for the evaluation of head trauma. Emergency operations on the cranium were mostly for relief of subdural and intracerebral hematomas and for elevation of depressed fractures. Interestingly, none of the 31 patients with intracranial tumors required an emergency operation, whereas all three with brain abscesses were operated on as surgical emergencies. Most of the emergency surgery on spinal cords was for traumatic fracture dislocations. Only two patients with protruded lumbar discs underwent laminectomy on an emergency basis. In 5 years, there were operations for 34 brain tumors, of which 28 were supratentorial and six in the posterior fossa (Table 3). Thus, the average was seven tumors per year, six supratentorial and one in the posterior fossa. Of the 31 tumors, only one was metastatic, a uterine adenocarcinoma. This does not reflect an aversion of neurosurgeons at the Mayo Clinic to operating on metastatic intracranial tumors: during the 5year period they dealt surgically with 125 such tumors in patients from all sources. In the management of trigeminal neuralgia, the open procedures used in 1970 and 1971 have been replaced by use of percutaneous radiofrequency. In the 5-year period, 19 aneurysms in 17 patients were dealt with surgically. All were supratentorial; none were in the vertebrobasilar circulation. All three arteriovenous malformations dealt with surgically were also supratentorial. The yearly incidence of lumbar disc protrusion requiring surgery ranged between 33 50
and 42, averaging 37 per year (Table 4). Of all procedures performed by neurosurgeons on Olmsted County residents, removal of a lumbar disc was the most frequent. It is noteworthy that no thoracic disc procedures were performed in the 5 years; this fact provides further evidence for the rarity of this lesion. In 1973 and 1974 there was a sharp decrease in the number of operations for lumbar disc ruptures combined with orthopedic fusion procedures. This may reflect the general trend of practice in the United States. Only one patient in Olmsted County had an operation for primary spinal cord tumor in the 5-year period, a neurofibroma at the L-2 level. Peripheral nerve surgery was performed infrequently by neurosurgeons (Table 5). Only two patients required sympathectomy, two underwent brachial plexus exploration, and one had a peripheral nerve tumor excised. The annual frequency of surgical treatment for some selected disorders is given in Table 6. Summary During 1970 through 1974, residents of Olmsted County, Minnesota, required intervention by neurosurgeons at the annual rate of 42/100,000 population for lumbar disc removal, six for cervical disc removal, and seven for brain tumor. Other disorders necessitated neurological surgery less frequently. There are no previous reports for comparison with this one. It is hoped that this study and similar investigations by others will provide a more definite basis for estimation of the composition of neurosurgical practice and the number of neurosurgeons needed in the United States. References 1. Hauser WA, Kurland LT: The epidemiology of epilepsy in Rochester, Minnesota, 1935 through 1967. Epilepsia 16:1-66, 1975 2. Kurland LT: Descriptive epidemiology of selected neurologic and myopathic disorders with particular reference to a survey in Rochester, Minnesota. J Chronic Dis 8: 378-418, 1958 3. Kurtzke JF, Kurland LT: The epidemiology of neurologic disease, in Baker AB, Baker LH (eds): Clinical Neurology, Volume 3. New York: Harper & Row, 1973, pp 1-80 4. Lesser RP, Hauser WA, Kurland LT, et al: Epidemiologic features of the Guillain-Barr6 J. Neurosurg. / Volume 46 / January, 1977
Community needs for neurosurgery syndrome: experience in Olmsted County, Minnesota, 1935 through 1968. Neurology 23:1269-1272, 1973 5. Odom GL: Neui'ological surgery in our changing times: the 1972 AANS presidential address. J Neurosurg 37:255-268, 1972 6. Percy AK, Elveback LR, Okazaki H, et al: Neoplasms of the central nervous system: epidemiologic considerations. Neurology 22:40-48, 1972 7. Sugar O, Mullah JF, Bucy PC: How many
J. Neurosurg. / Volume 46 / January, 1977
neurosurgeons? Surg Neurol 1:321-325, 1973 (editorial) 8. Whisnant JP, Fitzgibbons JP, Kurland LT, et al: Natural history of stroke in Rochester, Minnesota, 1945 through 1954. Stroke 2:11-22, 1971 Address reprint requests to: Glen G. Glista, M.D., c/o Section of Publications, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55901.
51
LEONARD T. KURLAND, M . D . , AND MARK L. JERECZEK
Mayo Clinic and Mayo Foundation, Rochester, Minnesota ~" To help determine neurosurgical needs within communities and within the nation, operations and diagnostic procedures performed by neurosurgeons on residents of Olmsted County, Minnesota, in the 5 years of 1970 through 1974, were tabulated. This county was studied because its medical records are virtually complete. Annual rates (per 100,000 population) were 42 for lumbar disc removal, six for cervical disc removal, and seven for brain-tumor therapy. Other less frequent occasions for neurological surgery are also tabulated. KEY WORDS epidemiology
9 neurosurgical m a n p o w e r 9 cerebral angiography 9 9 brain neoplasms 9 intervertebral disc displacement
HE existing number and the optimal number of neurosurgeons in the United States have been subjects of discussion among neurosurgeons and various governmental agencies for many y e a r s ) ,7 It has been estimated that in the United States there is one neurological surgeon per 100,000 population, but most of these specialists are in urban communities, particularly in the largest cities, and in academic and referral centers. Difficulties in determining an ideal number and pattern of distribution among the population include the uncertainty as to the number and variety o f diagnostic and surgical activities a neurological surgeon can be expected to p e r f o r m for a hypothetical average community of 100,000 people. We are reporting the number and type of procedures performed by neurosurgeons in a circumscribed population (Olmsted County,
T
46
Minnesota), over a 5-year period. We hope that this account will help to determine the neurosurgical needs of a community and provide young neurosurgeons with some idea of what procedures they may be called on to perform. S o u r c e o f Information
It is recognized that no single community can be considered as representative of the United States, since incidence rates, particularly for trauma, m a y vary widely with age, sex, race, automobile commuting practices, and industrial hazards. The experience in Olmsted County, Minnesota, provides incidence rates for many neurological and neurosurgical disorders in a defined community? The advantages of using the neurosurgical experience available in this area J. Neurosurg. / Volume 46 / January, 1977
Community needs for neurosurgery appear to outweigh the possible limitations with regard to its size, location, and population composition. Many of the estimates of incidence and prevalence of neurological diseases in the United States have come from previous studies of this community. 1,2,',6,8 The Mayo Clinic in Rochester has served for several decades as essentially the only source of medical care for this population. This unique medical record system, maintained for more than 40 years, readily identifies all medical encounters and diagnoses of local residents at the Mayo Clinic offices, affiliated hospitals (including emergency rooms), and home visits. In 70% of deaths among the local population, autopsy is performed by the Mayo Clinic Department of Pathology and Anatomy. The record-indexing system currently includes cases seen by the independent Olmsted Medical Group and other hospitals in and around Olmsted County. Since it is unlikely that any significant number of patients go elsewhere for diagnosis of serious illness or for any major surgery, the central data file maintained at the Mayo Clinic contains records of virtually all health care in the county population. Neurosurgical practice for the Olmsted County population is conducted almost exclusively at the Mayo Clinic facilities, since all neurosurgeons within 50 miles of Rochester are at the Clinic. There are currently seven staff neurosurgeons and 21 neurosurgical residents at the Mayo Clinic and its affiliated hospitals. Although each consultant may be expected to provide any neurosurgical service, there has been an increasing tendency in recent years toward subspecialization, particularly for pediatric and vascular surgery. The breadth of experience and variety of specialty interests represented by this staff preclude referrals elsewhere for care. The generally conservative group practice and ease of consultation with members of the Neurology Department and other specialists limit neurosurgical intervention to those cases most likely to respond to such procedures. Materials and Methods
Our study was based on the records of all neurosurgical diagnostic procedures and operations performed at the Mayo Clinic from 1970 through 1974 on patients who were J. Neurosurg. / Volume 46 / January, 1977
residents of Olmsted County, Minnesota, at the time. It should be recognized that the relatively small numbers of some procedures performed during this period make it difficult to produce rates that can be applied without substantial allowance for chance fluctuation. Although we considered extending the length of the study to 10 years to provide larger and presumably more stable rates, recent changes in neurosurgical practice dictated that the most recent 5 years of experience would best serve the purposes of this investigation. The estimated population of Olmsted County, Minnesota, at the midpoint of this study, July 1, 1972, was 87,955. The numbers given below can be converted to the frequency per 100,000 by multiplying the average number per year by the factor 1.14. The population studied is comparatively well educated, almost entirely Caucasian, and slightly younger than the United States population as a whole. The major occupational centers in Rochester are the Mayo Clinic, affiliated hospitals, and a large IBM assembly plant and research center. There is little that could be considered as heavy industry. Just outside Rochester there is suburban housing, but the rest of the county is rural and largely concerned with farming. This study includes only those patients upon whom a neurosurgeon performed a diagnostic procedure or neurosurgical operation. It does not include patients who consulted a neurosurgeon for evaluation only or who received nonsurgical treatment only, such as conservative treatment for a lumbar disc or observation of a closed head injury. Most patients who have a diagnostic procedure or operation performed by a neurosurgeon are first evaluated by a neurologist at the Mayo Clinic. In addition to all intracranial surgery, the neurosurgical department at the Mayo Clinic performs all carotid endarterectomies and all vertebral disc surgery. Some operations for trauma of the peripheral nerves are performed in cooperation with orthopedic surgeons, especially when associated with orthopedic injury to an extrem. ity. Release of the transverse carpal ligament for median nerve compression at the wrist (carpal tunnel syndrome) is performed on occasion by neurosurgeons but more often by the orthopedic surgeons who may be concerned with other problems involving the wrist joint of the same patient. Sympathetic ,t7
G. G. Glista, et al. TABLE t
TABLE 2
Number of Olmsted County residents on whom neurosurgeons performed diagnostic procedures or operations*
Number of diagnostic procedures performed by neurosurgeons on Olmsted County residents
Procedure
1970
1971
1972
1973
1974
elective emergency total
119 24 143
128 19 147
111 18 129
121 14 135
107 9 116
Procedure angiography* carotid retrograde brachial pneumoencephalography ventriculography subdural tap total
*Diagnostic procedures included cerebral angiography, pneumoencephalography, ventriculography, a n d subdural taps.
1970
1971
1972
1973
1974
68 44
65 40
57 40
56 42
57 43
24
25
17
14
14
11 4 1 84
17 2 1 85
10 2 0 69
5 4 0 65
3 2 2 64
*The numbers listed for angiography are n u m b e r of vessels studied, often more than one in a patient.
ganglionectomy is also performed by general surgeons, particularly when peripheral vascular reconstructive procedures are indicated. Likewise, some peripheral nerve biopsies and temporal artery biopsies are performed by members of other departments at the Mayo Clinic. Only when the above procedures were performed by a neurosurgeon were they included in this report.
Summary of Findings The number of Olmsted County residents who underwent neurosurgical diagnostic procedures and operations performed by neurosurgeons during the years 1970 through 1974 is given in Table 1, the number of diag-
TABLE 3
Major cranial procedures performed on Olmsted County residents* Lesion or Procedure tumors supratentorial glioma meningioma pituitary t u m o r craniopharyngioma ectopic pinealoma infratentorial acoustic neurinoma metastatic lesion glioma medulloblastoma rhizotomy or compression for trigeminal neuralgia brain abscess aneurysm arteriovenous malformation carotid endarterectomy elevation of depressed fracture acrylic cranioplasty hematoma intracerebral subdural acute chronic (burr-hole evacuation) m e m b r a n e (removal by craniotomy) shunt cerebrospinal fluid subdural-peritoneal
1970
1971
1972
3
12
4
3
3 2 1 1 1
3 1
1973
1974
(8)t
4
9 (6)t
1
11
1
1 1
2 1 1 1 2 1 2 2
3 2 1 2 1 3 3
2
1
3 (2) 1 7 (4)
1 1
5 (4) 2 (1)
7 (5) 2
6 (5)
1
5 (4) 1
5
2 (1) 2
3 5
3 3
1
1
2
I
1
1 2
3 (2) 2
5 (4)
8 (6)
2 (1) 9 (6) 1
7 (5)
*The n u m b e r of patients, if different from the n u m b e r of procedures, is given in parentheses. t O n e patient with glioma had three operations. 48
J. Neurosurg. / Volume 46 / January, 1977
C o m m u n i t y needs for neurosurgery nostic procedures performed in Table 2, and the number of major cranial operations in Table 3. The following other major cranial procedures were performed only once (or in only one patient) during the 5-year period: stereotaxic cingulectomy; craniectomy for osteomyelitis of the skull; operations for arachnoid cyst, p o r e n c e p h a l i c cyst, and craniosynostosis; stereotaxic hypophysect o m y for diabetic r e t i n o p a t h y ; transsphenoidal hypophysectomy for carcinoma of the prostate; treatment for acute epidural hematoma; repair of traumatic mastoid cerebrospinal fluid leak (twice in one patient); and stereotaxic t h a l a m o t o m y (twice in one patient). T h e n u m b e r o f vertebral neurosurgical procedures is listed in Table 4. Other vertebral procedures performed only once in 5 years included meningomyelocele repair, excision of lumbar dermal sinus with intradural exploration, and biopsy of vertebral body. The number of operations by neurosurgeons for peripheral nerve trauma and various miscellaneous procedures is given in Table 5. Other minor procedures performed infrequently in 5 years included insertion of Crutchfield tongs (6), excision of sebaceous scalp cyst (3), skull biopsy (2), closed reduction C4-5 fracture (1), excision of dermal sinus of scalp (1), and excision of traumatic arteriovenous fistula of scalp (1). Removal of lumbar discs was performed at only one level in most cases. A few of the patients in 1972, 1973, and 1974 chose chemonucleolysis of the lumbar disc rather than an open operation. All patients who had chemonucleolysis were candidates for an open procedure and were offered chemonucleolysis as an option during a clinical trial. As explained, since all cervical and lumbar disc surgery at the M a y o Clinic is performed by the Department of Neurosurgery, the numbers reported probably reflect accurately the incidence of surgically treated disc disease in residents of Olmsted County.
Discussion
Table 2 shows t h a t the n u m b e r of .pneumoencephalograms performed declined in 1973 and 1974. This decline is most probably explained by introduction of the computerized t o m o g r a p h y (CT) scanner at this clinic in July, 1973. Patients with such J. Neurosurg. / Volume 46 / January, 1977
TABLE 4 Vertebral procedures performed by neurosurgeons on Olmsted County residents
Lesion or Procedure
1970 1971 1972 1973 1974
lumbar disc removal 38 with fusion 12 decompression for spondylosis 0 cervical disc removal 2 decompression for spondylosis 1 spinal cord tumor primary 0 metastatic 1 spinal exploration for trauma 2
37 14
35 9
42 1
33 4
0
1
0
0
6
9
5
4
1
0
2
4
0 0
0 0
1 1
0 1
4
2
1
0
problems as presenile dementia or seizures, who previously might have u n d e r g o n e pneumoencephalography, are being scanned by CT which demonstrates the ventricular system well. TABLE 5 Peripheral nerve surgery and other miscellaneous procedures performed by neurosurgeons on Olmsted County residents*
Lesion or Procedure temporal artery biopsy tracheostomy percutaneous cordotomy ulnar nerve translocation median nerve decompression for carpal tunnel syndrome sympathectomy peripheral nerve tumor radiofrequency lesion of Gasserian ganglion brachial plexus exploration exploration or repair of peripheral nerves
1970 1971 1972 1973 1974 2 3
8 1
1 4
7 1
8
12
3
3 (2) 2
1 1
1
2 (1)
1
5 (3)
1
If
1
1
2
2
1 7
1
1
*The number of patients, if different from number of procedures, is given in parentheses. tNeurofibroma in flank. 49
G. G. Glista, e t al. TABLE 6 Annual frequency per 100,000 population of some selected operations
Operation
Frequency per 100,000
cerebral angiography brain tumor aneurysm arteriovenous malformations carotid endarterectomy lumbar disc removal cervical disc removal ulnar nerve translocation elevation of depressed fracture evacuation of intracerebral hematoma
66.8 7.1 4.3 0.9 2.5 42.2 5.9 2.3 3.4 1.1
Most frequent among the emergency procedures carried out was cerebral angiography for the evaluation of head trauma. Emergency operations on the cranium were mostly for relief of subdural and intracerebral hematomas and for elevation of depressed fractures. Interestingly, none of the 31 patients with intracranial tumors required an emergency operation, whereas all three with brain abscesses were operated on as surgical emergencies. Most of the emergency surgery on spinal cords was for traumatic fracture dislocations. Only two patients with protruded lumbar discs underwent laminectomy on an emergency basis. In 5 years, there were operations for 34 brain tumors, of which 28 were supratentorial and six in the posterior fossa (Table 3). Thus, the average was seven tumors per year, six supratentorial and one in the posterior fossa. Of the 31 tumors, only one was metastatic, a uterine adenocarcinoma. This does not reflect an aversion of neurosurgeons at the Mayo Clinic to operating on metastatic intracranial tumors: during the 5year period they dealt surgically with 125 such tumors in patients from all sources. In the management of trigeminal neuralgia, the open procedures used in 1970 and 1971 have been replaced by use of percutaneous radiofrequency. In the 5-year period, 19 aneurysms in 17 patients were dealt with surgically. All were supratentorial; none were in the vertebrobasilar circulation. All three arteriovenous malformations dealt with surgically were also supratentorial. The yearly incidence of lumbar disc protrusion requiring surgery ranged between 33 50
and 42, averaging 37 per year (Table 4). Of all procedures performed by neurosurgeons on Olmsted County residents, removal of a lumbar disc was the most frequent. It is noteworthy that no thoracic disc procedures were performed in the 5 years; this fact provides further evidence for the rarity of this lesion. In 1973 and 1974 there was a sharp decrease in the number of operations for lumbar disc ruptures combined with orthopedic fusion procedures. This may reflect the general trend of practice in the United States. Only one patient in Olmsted County had an operation for primary spinal cord tumor in the 5-year period, a neurofibroma at the L-2 level. Peripheral nerve surgery was performed infrequently by neurosurgeons (Table 5). Only two patients required sympathectomy, two underwent brachial plexus exploration, and one had a peripheral nerve tumor excised. The annual frequency of surgical treatment for some selected disorders is given in Table 6. Summary During 1970 through 1974, residents of Olmsted County, Minnesota, required intervention by neurosurgeons at the annual rate of 42/100,000 population for lumbar disc removal, six for cervical disc removal, and seven for brain tumor. Other disorders necessitated neurological surgery less frequently. There are no previous reports for comparison with this one. It is hoped that this study and similar investigations by others will provide a more definite basis for estimation of the composition of neurosurgical practice and the number of neurosurgeons needed in the United States. References 1. Hauser WA, Kurland LT: The epidemiology of epilepsy in Rochester, Minnesota, 1935 through 1967. Epilepsia 16:1-66, 1975 2. Kurland LT: Descriptive epidemiology of selected neurologic and myopathic disorders with particular reference to a survey in Rochester, Minnesota. J Chronic Dis 8: 378-418, 1958 3. Kurtzke JF, Kurland LT: The epidemiology of neurologic disease, in Baker AB, Baker LH (eds): Clinical Neurology, Volume 3. New York: Harper & Row, 1973, pp 1-80 4. Lesser RP, Hauser WA, Kurland LT, et al: Epidemiologic features of the Guillain-Barr6 J. Neurosurg. / Volume 46 / January, 1977
Community needs for neurosurgery syndrome: experience in Olmsted County, Minnesota, 1935 through 1968. Neurology 23:1269-1272, 1973 5. Odom GL: Neui'ological surgery in our changing times: the 1972 AANS presidential address. J Neurosurg 37:255-268, 1972 6. Percy AK, Elveback LR, Okazaki H, et al: Neoplasms of the central nervous system: epidemiologic considerations. Neurology 22:40-48, 1972 7. Sugar O, Mullah JF, Bucy PC: How many
J. Neurosurg. / Volume 46 / January, 1977
neurosurgeons? Surg Neurol 1:321-325, 1973 (editorial) 8. Whisnant JP, Fitzgibbons JP, Kurland LT, et al: Natural history of stroke in Rochester, Minnesota, 1945 through 1954. Stroke 2:11-22, 1971 Address reprint requests to: Glen G. Glista, M.D., c/o Section of Publications, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55901.
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