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Posterior Fossa Epidermoid Tumors_ Assessment and Surgical Management


									  Posterior Fossa Epidermoid Tumors: Assessment
                       and Surgical Management
Omar Y. Hammad, MD, Ali Kotb Ali, MD, Khaled El Bahy, MD, Mohammed
                 El-Sayed, MD, Emad Ghanem, MD,
                    Adel Hussien El-Hakim, MD
                Neurosurgery Department, Ain Shams University, Cairo, Egypt

     Objectives: The management of a series of 15 patients operated upon for posterior
          fossa epidermoid is reviewed. We discuss the rationale for a comprehensive
          management of posterior fossa epidermoids whether aggressive radical
          excision or conservative surgery.
     Methods: A retrospective analysis of 15 patients (8 men, 7 women) with posterior
          fossa epidermoid have been operated upon at neurosurgery department of
          Ain Shams University hospital through the last four years. Age ranged
          between 20 years and 50 years (mean age 45.5 years). MRI was used for all
          patients. We classified patients into 4 groups: CPA-epidermoid (n = 8),
          fourth ventricle epidermoid (n = 3), cerebellar epidermoid (n = 2) and basal
          posterior fossa epidermoid (n = 2). Five surgical approaches were carried
          out: Midline suboccipital (n = 2), retromastoid suboccipital (n = 4),
          infratentorial-supracerebellar (n = 2), staged retromastoid with
          frontotemporal approach (n = 4) and transvermian (n = 3). Follow-up
          duration ranged between 6 months and 4 years (mean, 3.2 year).
     Results: Clinical features of epidermoid and surgical approaches varied according
           to location and growth pattern. Thirteen patient out of 15 have showed total
           removal (86.7%); 7 cases with CPA epidermoid (87.5%), one case with
           basal posterior fossa epidermoid (50%), all cases with fourth ventricular
           epidermoid (100%) and cerebellar epidermoids (100%). Cranial nerves
           showed varying degree of involvement and improvement. Infrequent curable
           complications (33%) were observed. Patients were placed into one of three
           groups according to their follow-up condition: excellent category (10
           patients), good category (3 patients), and 2 patients showed persistent
           neurological deficit. The recurrence-free survival rate was 100% during the
           4 years follow up.
     Conclusion: The main problems in the management of epidermoids remain
          misdiagnosis, incomplete removal and delayed detection of recurrences.
          MRI P-D weighted image is superior in detection of epidermoids. The
          location and extension of epidermoids play a major role in planning surgery
          and patient prognosis. Cranial nerve deficits are not a prognostic factor for
          surgical dissection of epidermoid, but it is a cranial nerve type response to
          the surgical trauma. Radical total removal of epidermoids preserving
          neurovascular structures is recommended.
     Key Words: Epidermoid, posterior fossa, neuroimaging, surgical treatment.

         Epidermoid tumors are slow growing benign tumors. They have unique
growth pattern as they extend and spread into the subarachnoid space and cisterns
remaining silent for a long period(3,4,32,41). They may arise from displaced dorsal
midline ectodermal cell rests between the third and fifth weeks of embryogenesis
during neural tube closure. However, CPA and parasellar location could be explained
by the result of proliferation of multipotential embryogenic cell rests or lateral
displacement of ectodermal cells by the developing otic vesicles(5,13).

         Intracranial        epidermoid    tumors   are   histologically    benign     congenital
neoplasms. They grow by the accumulation of keratin and cholesterol, which are
breakdown products created by the desquamation of epithelial cells(1).

         Epidermoids           account    for   approximately    0.1%      of   all   intracranial
         (7,8,16,17,30,33)                                (28)
tumors                       and   7% of CPA tumors          . CPA epidermoids constitute
approximately 60% of all intracranial epidermoids and are the third most common
tumors of the CPA after acoustic neuromas and menengiomas(2). The second most
prevalent location in the posterior fossa is the fourth ventricle accounting for 5-18%
of all intracranial epidermoids(23). Nevertheless, posterior fossa epidermoid are often
the most troublesome to cure because of their insinuating growth into different spaces
and cisterns in addition to engulfing cranial nerves and vessels which make it difficult
for radical excision(45). It is not surprising that, prior to the microsurgical era,
operative mortality ranged from 20% to 57%(34). However, although the great
advances in neuroimaging techniques, still neurosurgeons face a strong challenge in
managing such tumors, whether an aggressive surgery carrying a high morbidity and
mortality or a conservative subtotal tumor excision carrying a low morbidity low
mortality with a higher rate of recurrence, which of these should be perscued.

Patients and Methods:

         Fifteen patients with posterior fossa epidermoids underwent surgical treatment
through the last four years at the department of neurosurgery, Ain Shams University
hospitals. Age ranged between 20 years and 50 years (mean age, 45.5 yrs.), they
included 8 males and 7 females (Fig. 1). The diagnosis and follow-up assessment was
determined using CT and MRI. Patients have been followed-up for a period ranged
between 6 months and 4 years (mean 3.2 yrs).


Clinical Course
       The interval between onset of symptoms and diagnosis ranged between 3
months and 10 years. In five patients the interval ranged between 5-10 years, while in
10 patients the interval ranged between 3 months to 4 years (Fig. 2). Two peaks of
incidence were recognized at second and fifth decade of life.

       We classified patients into 4 groups: CPA-epidermoid (n = 8), fourth ventricle
epidermoid (n = 3), cerebellar (n = 2) and basal posterior fossa (n = 2) (table 1).

       CPA epidermoids tended to express cranial nerve deficits and brain stem
dysfunction, while supratentorial extension expressed picture of increased intracranial
tension, visual dysfunction, and seizures (table 2). In cerebellar epidermoid, all
patients presented with cerebellar dysfunction; (ataxia, nystagmus, dysmetria), while
fourth ventricular epidermoid presented with increased intracranial tension and brain
stem dysfunction (table 3).

Neuroimaging Evaluation

       CT brain was performed for all patients presented with posterior fossa
epidermoid. It revealed a hypodense area at the site of epidermoid in all patients with
a fine enhancement in only 2 patients. MRI brain with T1 weighted image showed
epidermoids as hypointense area while in T2 weighted image epidermoids appeared
hyperintense. Proton density is the key for diagnosis where epidermoids appear as non
homogeneous hyperintensity in all patients. With IV gadolinium it doesn't take any
contrast enhancement. MRI technique is quite superior in depicting the epidermoids;
the site, the extent and the relation to the neurovascular structures.

Operative approach

       Tumor location and its growht pattern, plays an important role in determing
the type of surgical approach. Five conventional approaches were performed for 15
cases with posterior fossa epidermoid. Midline suboccipital approach was performed
in 2 cases with cerebellar epidermoids, transvermian approach in 3 cases with fourth
ventricular epidermoids while 2 cases of CPA epidermoids with mesencephalic
extension were carried out through infratentorial-supracerebellear approach. Four
cases with pure CPA epidermoids were performed through retromostoid approach.
Staged retromastoid with frontotemporal approach was performed in 3 cases with
parasellar extension (Fig. 3) and 1 case with suprasellar extension (table 4). At the end
of the surgery after removal of epidermoid contents, copious irrigation of saline with
hydrocortisone (2 gm) in addition to perioperative parentral dexamethasone was used
regularly to prevent chemical meningitis.

Operative Results

        Using sharp microscopic dissection techniques leaving only firm portions of
capsule adherent to neurovascular structures and working through the space created
by the tumor removing all tumor contents was our policy in treating this type of
tumors. Radical excision leaving only small portions of firm adherent capsule has
been achieved in (13) patients (86.7%) (table 5). Patients with cerebellar epidermoids
(Fig. 4) showed total radical removal (100%). Hardly, total radical excision was
achieved in 3 patients (100%) with fourth ventricular epidermoids (Fig. 5), one patient
(50%) with basal posterior fossa epidermoid (Fig. 6) and 7 patients (87.5%) with CPA
epidermoids (Fig. 7). Nevertheless, subtotal excision leaving large portions of capsule
or distant contents of epidermoids was observed in only two patients (13.3%) with
temprobasal extension.

        Epidermoids have the tendency to adhere to neurovascular structures.
According to type of epidermoids and its extension, involvement of cranial nerves are
determined. Sharp meticulous microscopic dissection was performed to release firm
adherent capsule portions from cranial nerves. Table (6) shows the different responses
of cranial nerves to surgical dissection. The optic nerves showed the least
improvement (20%). The best response was recorded for trigeminal, hypoglossal, and
abducens nerves (100%, 100% and 83%) respectively. Other cranial nerves showed
varying degree of dysfunction.

        Although surgical removal of epidermoids and dissection carries high
morbidity due to the specificity of epidermoid capsule to adhere to neurovascular
structures, but the meticulous surgical techniques lessen the high incidence of

        Patients were placed into one of three groups according to their follow up
condition relative to their preoperative status (table 7). The excellent category
includes patients whose status was maintained or improved to a normal neurological
condition without persistent symptoms. Ten patients (66.5%) with epidermoid tumors,
met these requirements. Good category, includes patients developed overall
improvements, but with minor residual deficits. Three patients with epidermoids
(20%) fell into this group. Those patients whose neural status remained unchanged
after surgery included one patient with suprasellar extension and another patient with
fourth ventricular epidermoid (13.5%).


       Minor curable complications were noticed through 15 patients with posterior
fossa epidermoids. Five patients (33%) experienced combination of postoperative
complications displayed in table (8). Three patients developed aseptic meningitis,
with communicating hydrocephalus. Two of them showed pseudomenengeocele with
CSF leak. They were cured with V-P shunt. The following complications occurred
infrequently seizures (2 cases), wound infection (1 case), subdural hematoma (1 case),
(underwent surgical evacuation). There were no perioperative deaths.


       CPA epidermoid constitutes 60% of all intracranial epidermoids and are the
third most common tumors of CPA after acoustic schwanoma and meningioma(2). The
fourth ventricular epidermoid is the second most common epidermoid of posterior
fossa. It constitutes 5-18% of all intracranial epidermoids(23).

       Lepoire and Pertuiset(22) described a classification for posterior fossa
epidermoids consisting of three groups based on the role of blood vessels in tumor
migration;    vertebrobasilar    artery,   carotid   artery,   and   choroidal   arteries
(intraventricular type). Obrador and Lopez-Zafra(27) suggested their classification
according to the clinical and surgical data as suprasellarchiasmatic,         parasellar-
sylvian, retrosellar-cerebellopontine, and basilar posterior fossa epidermoids.
However, such classification doesn't represent the true extension of the tumor. After
the advent of CT scan, Yasargil(45) added three other groups to the former
classification; anterosellar-frontobasal, mesencephalic-pineal and intraventricular. He
recorded that epidermoids do not extend much post the midline, only might bulge
across the midline but not to involve actively the contralateral subarachnoid spaces(45).
Fleming and Botterell(13), stated lateral suboccipital epidermoid, while Gormley(15)
and Lunardi(24), described cerebellar and CPA-clival epidermoids. At 1996, Samii et
al.(34), introduced another classification which emphasize tumor extension, tumor size
and the surgical implications, according to posterior fossa compartments: the first
compartment lies between the undersurface of the tentorium and fifth cranial nerve,
the second from the trigeminal nerve to the seventh-eighth cranial nerves complex,
the third down to the lower cranial nerves and the fourth floor from these to the
foramen magnum.

         We classified our cases into 4 groups; CPA epidermoids (8 cases) fourth
ventricular (3 cases), basal posterior fossa (2 cases) and cerebellar epidermoids (2
cases) (table 1). We noticed that, CPA epidermoid represented the most common type
of posterior fossa epidermoid (53%), it showed supratentorial extension in 2 cases and
as infratentorial extension (mesencephalic) in another 2 cases. Others, observed
suprasellar, temprobasal and mesencephalic epidermoids as a separate category not as
a spread or extension from CPA epidermoid(2, 27, 34, 45). We observed fourth ventricular
epidermoids in 3 cases (20%) and cerebellar epidermoid in 2 cases (13%), which are
parallel to literature observations(2, 15, 23, 24, 27, 34, 45).

         Two peaks of incidence were noticed for posterior fossa epidermoids, at the
2 and 5th decade of life. The younger group is explained by the embryogenic disorder
while the older one might arises from metaplasia of multipotent cells(5, 13, 26, 39, 40).

         The relatively prolonged history and silent period could be explained by the
slow growth of tumor and its slow insinuation into already opened subarachnoid
spaces and CSF cisterns. With tumor migration and spread, it involves more cisterns
and neurovascular structures, being the actual alarm for patients to seak for medical
advice. Our series confirm that the most common presentation of posterior fossa
epidermoid are cranial nerves involvement and cerebellar dysfunction which is in
agreement to observations in literatures(11,12,19,25). Some recorded tinitus, trigeminal
neuralgia, and hemifacial spasm or weakness(19). Others, recorded chronic history of
recurrent aseptic menengitis which could be explained by the spontaneous rupture of a
highly irritative cyst contents into the subarachnoid space precipitating the
development of communicating hydrocephalus(1,9,35,45).


         MRI is highly sensitive to epidermoid tumor determening the full extension of
the tumor and its relation to surrounding neurovascular structures. However, MRI
stands out from other imaging techniques since it allows the clear differentiation of
epidermoids from dermoid and arachnoid cysts or normal cisterns. PD weighted
image is the sequence of choice for this purpose(18,20,29,38,43). Diffusion - weighted(34)
and proten-density(37) imaging modalities are recommended to distinguish
epidermoids from cerebrospinal fluid.

       With the aid of modern imaging techniques, surgical approaches could be
planned, properly. Five standard surgical approaches were performed; retromastoid
approach, midline suboccipital, infratentorial-supracerebellar, staged frontotemporal
with retromastoid approach and transvermian approach. Midline suboccipital
approach was optimum for cases of cerebellar epidermoids, while in fourth ventricular
epidermoid, transvermian approach was carried out. Mesencephalic region was
accessible through infratentorial-supracerebellar approach. Nevertheless, retromastoid
approach was preferred for CPA epidermoids. Suprasellar or temprobasal (parasellar)
epidermoid extension (4 cases) were operated upon through staged retromastoid and
frontotemporal approaches to minimize brain retraction and neurovascular
compromise. However, Yasargil(45) recommends a single retromastoid approach for
CPA epidermoids with supratentorial extension, even in cases with hour glass tumors
extending into both posterior and middle cranial fossa. He assumes that he follows the
space created by the tumor. Samii(34) advocates the use of endoscope to reach the
blind areas through a single retromastoid approach, reducing the need for extensive
cranial base approaches. Nevertheless, others prefer the use of combined or staged
supratentorial and infratentorial approaches reducing aggressive brain retraction or
neurovascular compromise and accomplishing good tumor removal(2,37).

Extent of Surgical Removal

       Total removal was accomplished in 13 patients (86.7%) removing all tumor
contents, tumor capsule, leaving only a small portions of firm adherent capsule. All
cases of cerebellar epidermoid and pure type CPA epidermoid expressed total
removal (100%). Nevertheless, fourth ventricular epidermoids showed difficult total
removal (100%) where tumor capsule was firmly adherent to the pia of brainstem or
neurovascular structures leaving small adherent capsule, while supratentorial
extension showed only total removal in 2 cases (50%).

       In literatures, total removal ranged between 0-97% with patient mortality rate
between 0-12%, while tumor recurrence varried between 0-30%(2,6,10,14,21,23,31,37,44,45,46).
Berger and Wilson(6) in a series of 13 cases with CPA epidermoids, achieved subtotal
removal in all cases with no mortality nor recurrence on follow-up (mean 4.5 years).
Rubin and his colleagues(31), recorded 4 cases out of 7 (57%) as total removal with no
mortality, nor recurrence on follow-up (mean 4.6 years). On follow-up (mean 8 years)
of 15 patients with CPA-epidermoid, Yamakawa et al.(44), carried out total removal in
(47%) with mortality rate (6.6%) and (20%) recurrence rate. Through 1967 to 1988
Yasargil et al.(45), studied 35 cases with posterior fossa epidermoids, achieved total
removal in 34 cases (97%) with (2%) mortality and recurrence free on mean follow up
5.7 years. Only one case had a firm adherent capsule to the basilar artery and
perforators, any trial of removal would carry a high risk. On 30 patients with CPA
epidermoids, deSouza and his colleagues(10) could not perform a total removal of
epidermoid cyst, except in only (18%) of cases with (3.3%) mortality.They observed
high recurrence rate (13.3%) through 5 years mean follow-up. Lunardi et al.(23),
published their data on 17 patients with CPA epidermoid, they achieved a total
removal in only (35%) of patients, but with high mortality rate (12%), high recurrence
rate (30%) at mean follow-up of 9 years. Zhou(46) in his series, reported 4 recurrences
out of 68 patients (5.9%) at follow-up 5-20 years. On six years follow-up, Altschuler
and his colleagues(2), found no recurrences with total or near total removal in 16 cases
out of 17 (94%). They recommended aggressive total excision especially in the first
operation, that can improve outcome and reduce recurrence, as the second surgery
becomes very difficult due to intense adhesions and arachnoiditis increasing
morbidity and mortality(2).

       Fukushima(14) in a series of 120 cases with posterior fossa epidermoids, he
agreed with Yasargil opinion that total aggressive resection using sharp microscopic
dissection yielded satisfactory results. Samii and his colleagues(34), published their
data on 40 patients with CPA epidermoids, achieved total radical removal in (75%) of
patients, with low mortality rate (2.5%). On a mean follow up period (5.7 years), they
observed radiological and clinical recurrence in (7.5%) of patients. Talachi et al.(37),
recorded total removal in 16 cases (57%) leaving distant fragments in 12 cases (43%).
On eight years follow-up 30% of cases who underwent subtotal removal showed
recurrence increased up to 35% at 13 years follow up(37).

       Recent publication of Kobata et al.(21) series, on 30 cases with CPA
epidermoid, they recorded total removal in (56.7%) of cases with tumor regrowth rate
(6%) in average follow-up period of 11.5 years.


       Epidermoids are tumors of time dependent recurrence, need a long follow-up.
Although our series have short follow-up (ranged from 6 months to 4 years, mean 3.2
yrs), we noticed no recurrence, even those cases with residual firm capsule or with
distant fragments on follow-up CT scan or MRI brain. Radiologically, as brain re-
expansion is extremely slow and incomplete, which is misleading for extent of tumor

         Sharp, patient, and meticulous microscopic dissection of firm portions of
capsule, lessen the high risk of morbidity and mortality. Nevertheless, aggressive total
removal whenever it is possible, is recommended avoiding spilling of tumor material
and using copious irrigation of surgical field with saline and hydrocortisone (2gm) to
lessen the possibility of aseptic meningitis and hydrocephalus. Stein(36), suggests that,
the best attempt at removal of the contents as well as the capsule should be performed
but not to the point of sacrificing vital structures.

         We agree with conclusions in literatures, that recurrences are associated with
extensive lesions, and incomplete initial resection. Although some authors have
reported excellent results in patients undergoing multiple operations due to
recurrence(33,42,44), others reported less satisfactory results(2,37). The time of the second
surgery for cases with recurrences still under big debate, whether it should be
performed on radiological recurrence or after the onset of symptoms. Nevertheless,
there is general agreement to interfere in cases with recurrent symptoms with clear
radiological evidence(2,6,45) that follow-up CT or MRI brain may pose doubts because
brain re-expansion is extremely slow and incomplete(37).


         Infrequent curable minor complications in 5 patients (33%) and no
perioperative deaths were observed. V-P shunt was a good solution for 3 patients
developed communicating hydrocephalus. Antiepileptics controlled seizures in 2
patients. Surgical evacuation of a subdural heamatoma was done for a patient after
excision of temprobasal epidermoid. Samii et al.(34), recorded two cases of CSF leak,
were treated by lumbar drainage, one case of aseptic meningitis treated with surgical
revision, and one patient developed hydrocephalus postoperatively, received V-P

Clinical Outcome

         Total radical excision of posterior fossa epidermoids leaving only small
portions of adherent capsule in 13% patients (86.7%) with overall postoperative
improvements with or without minor residual deficits in (86.5%) of patients, are
comparable to literature observations(2,6,13,14,21,34,37,39,40,41,45,46). Yasargil et al.(45)
reported (86%) of cases in good to excellent condition, with 2 cases died at the time
of follow-up. One patient developed basilar artery thrombosis during preoperative
angiography, became debilitated, and died postoperatively at the time of follow-up.
Another patient was in coma preoperatively due to brain stem compression by the
tumor, did not improve postoperatively and died one year later. One patient became
worse (2%) and 2 patients (6%) remained unchanged. Samii and his colleagues(34),
observed that (40%) of cases showed excellent condition, increased to (92.5%) at
follow-up time. At discharge, 7 cases (18%) showed fair condition, dropped to only
one case (3%) at follow-up time, while one case (3%) required nursing assistance.
Another one case had a very large bilateral cyst to brainstem associated with acoustic
neurinoma, died some weeks after surgery. In Kobata et al.(21) series, 15 cases (50%)
expressed excellent condition, increased to 26 cases (87%) at follow-up time, while 4
cases (13%) showed good condition with no mortality.


        Although epidermoids are benign tumors their unique growth pattern and
migration through CSF cisterns make their management chalangeble. The main
problems in the management of epidermoids remain misdiagnosis, incomplete
removal and delayed detection of recurrences. MRI-PD weighted images are superior
in detection and differentiation of epidermoids from other lesions. A classification
system for epidermoids, facilitate patient assessment, surgical plane and determines
patient prognosis. Epidermoids with supratentorial extension carry higher morbidity
and shows incomplete surgical removal while fourth ventricular tumor carry higher
risks of surgical complication. The goal in treating epidermoids must be radical
excision leaving only firm adherent portions of capsule to neurovascular structures.
Serial MRI studies allow better assessment and early detection of recurrences.
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                                                                     Male       Female

                       No of patient     6
                                                     II              III              IV            V
                                                                           Decade of life

                                                    Fig. (1): Age and sex distribution.

      No of patients



                                             0-1y             1-2y               2-3y            3-5y        5-10y
                                                                 Symptoms duration (years)

Fig. (2): The interval duration between the onset of symptoms and

      Table (1): Classification of posterior fossa epidermoids.

                                 Type                     No.         %        Pure              Extension           No.
   CPA                                                    8          53          4         Suprasellar/chiasmatic    1
                                                                                           Parasellar/temprobasal    1
                                                                                           Mesencephalic/pineal      2
   Basal post fossa                                       2          13           -        Parasellar/temprobasal    2
   Fourth ventricular                                     3          20          3                      -
   Cerebellar                                             2          13          2                      -
   Total                                                  15

     Table (2): C/P of CPA and basal post fossa epidermoids.
                                      CPA (n = 8)
                                                                        Basal post fossa
 Symptoms /signs          Pure        SS*          PS**     MC***
                                                                             (n = 2)
                         (n = 4)    (n = 1)       (n = 1)   (n=2)
   Headache                 3           1           1         1                   1
   Visual                   1           1           1         -                   2
   Diplopia                 1           1           1         1                   2
   Seizures                 -           -           1         -                   1
   Tinitus                  2           1            -        1                   1
   Facial pain              3           1           1         -                   1
   Facial weakness          3           1            -        1                   1
   Hypoacousia              2           1            -        1                   -
   Hemiparesis              1           -           1         1                   1
   Gaiat ataxia             2           1           1         1                   -
   Nystagmus                1           -           1         -                   -
   Dysmetria                1           -            -        -                   -
   Dysarthria               1           -           1         -                   -
   Dysphagia                -           1            -        -                   1

* SS = Supra sellar.   ** PS = Parasellar.         *** MC = Mesencephalic.

   Table (3): C/P of cerebellar and fourth ventricular epidermoids.

     Symptoms /signs                Cerebellar (n = 2)              4th ventricular (n = 3)
   Headache                                   1                               3
   Diplopia                                   -                               2
   Hypoacousia                                -                               1
   Gait ataxia                                2                               2
   Dysmetria                                  2                               2
   Nystagmus                                  2                               2
   Dysarthria                                 -                               2
   Dysphagia                                  -                               2
   Hemiparesis                                -                               2

                       Table (4): Surgical approaches.
                                                                                  CPA/Basal post. fossa
                    Tumors                            Fourth          Pure
                                   Cerebellar                                     PS        SS
                                                    ventricular       CPA                            MC           Total
                                     (n = 2)                                      (n =      (n =
Approches                                             (n = 3)     (n = 4)                           (n = 2)
                                                                                   3)        1)

1. Mid subocipital                     2                 -             -           -            -      -           2
2. Retromastoid                         -                -             4           -            -      -           4
3.       Retromast             +        -                -             -           3            1      -           4
4. ITSC*                                -                -             -           -            -     2            2
5. Transvermian                         -                3             -           -            -      -           3

* ITSC infratentorial supracerebellar.

                              Table (5): Extent of surgical removal.

            Tumor types                     No.      Total excision          %                              %

     CPA                                     8               7             87.5             1              12.5

                  Pure                       4               4             100              -
                  S.S                        1               1             100              -
                  P.S                        1               -               -              1              100
                  M.C                        2               2             100              -                 -

     Basal posterior fossa                   2               1               50             1              50

     Fourth ventricular                      3               3             100              -

     Cerebellar                              2               2             100              -

                  Total                      15              13            86.7             2              13.3

     * SS = Supra sellar.                   ** PS = Parasellar.                    *** MC = Mesencephalic.
                       Table (6): Cranial nerves response.

                                                   Postoperative results
Cranial      Preoperative     Postoperative
                                              Improvement          Unchanged
nerves       dysfunction       dysfunction
                                              No       %           No      %
  II nd            5                -         1        20          4       80
  III rd           3               1          3        75          1       25
  V th             7                -         7       100          -       -
 VI th             5               1          5        83          1       17
 VII th            6               2          6        75          2       25
 VIII th           5                -         3        60          2       40
IX th - X          4                -         3        75          1       25
 XII th            4                -         4       100          -       -

                            Table (7): Clinical outcome.

                         Condition                   No.           %
            Excellent                                10           66.5
            Good                                      3           20
            Unchanged                                 2           13.5

                   Table (8): Postoperative complications.

                        Complications                       No.
                Meningitis                                   3
                Hydrocephalus                               3
                CSF leak                                    2
                Seizures                                    2
                Wound infection                             1
                Subdural heamatoma                          1
                Hemiparesis                                 2

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