Slide 1. 11th Virtual International Conference of the Neurosurgery Research Listserv and the World Neurosurgery Webinar Conference 2021, presented by Mauro Segura, Neurología Segura Director, Morelia Mexico 2021 Slide 4. Epidermoid cysts are slow-growing brain tumors of embryonic origin that manifest later in life.1 The anterolateral cisterns of the brainstem is its most frequent location.2 They represent approximately 1% of intracranial tumors.1 They are present in about 2% of patients presenting as a first symptom a trigeminal neuralgia.2 The study of choice is a high definition MRI Slide 5. We present our experience and philosophy on the surgical approach based on three principles: Preserve the life of the patient. Do not damage the nerve and vascular structures adjacent to the surgical site to avoid neurological sequelae and complications inherent to surgery. Eliminate the cause of compressive neuropathy and relieve symptoms. Slide 6.For this presentation we focus primarily on the anterolateral location of the brainstem of Epidermoid Cyst. Slide 7. Our surgical technique in 10 steps. 1.Lateral decubitus positioning with head rotation 1 inch skin incision in the retromastoid region 2.Musculoskeletal plane dissection to reach the surface of the skull 3.Infra-asterional craniectomy <2cm 5. Durotomy in "<" or ">" 6. Depletion of CSF from the posterior fossa without brain retraction 7. Debulking and tumor resection 8. Treatment of the implant area 9. Hemostatic review of the microsurgical area 10.Hermetic duroplasty and soft tissues Slide 21. Our series of EC cases in the ALCs of the brainstem is one of the largest published in Latin America and, based on the excellent long-term results obtained, we propose this minimally invasive microsurgical approach as the best treatment. Comprehensive anterolateral cisterns of the brainstem as a 3D space concept Non-septate but monocompartmental, non-infiltrative towards the adjacent arachnoid Complete or subtotal excision without implant zone is the goal in the first surgery Due to the rarity of the entity, we recommend that the neurosurgeon interested in treating this type of tumor be trained in laboratories with cadavers, with software for 3D virtual surgery and under the tutelage of an expert neurosurgeon to resolve contingencies that may arise during the curve learning. Neurología Segura Medical Center www.neurologiasegura.net

1. Epidermoid Cyst of the Posterior Fossa
Mauro Segura, MD, PhD
Adriana F. Segura-Zenón, MD, Aarón G Munguía-Rodríguez, PhD
Neurología Segura Medical Center, Morelia, Mexico
Dec 4th, 2021 Investigación
Segura
"Improving Outcomes, Output & Cost"
December 4-5, 2021
11th Virtual International Conference of the
Neurosurgery Research Listserv

2. Jan 2011-Oct 2021
n= 2210
Simple n= 2081 Combined n= 129
Glossopharyngeal Neuralgia
n= 62
Hemifacial Spasm
n= 124
Trigeminal Neuralgia
n= 1841 (83%)
Other Neuropathies
n= 54
Classical n= 1286 Secondary n= 320 (14,4%) Idiopathic n= 235
Epidermoid Cyst n= 33 (1,4%)
Hyperactive Dysfunction Syndrome of Cranial Nerves
n= 2210
Other Etiologies n= 287
Infratentorial n= 26
(78%)
IT +ST n= 7
Introduction

3. Secondary trigeminal neuralgia
Age distribution
0 5 10 15 20 25 30 35 40
Postherpetic
Epidermoid cyst
Meningioma
Dental process
Neuroma
Multiple sclerosis
Temporomandibular dysfunction
Maxillofacial trauma
Psychological
Arteriovenous malformation
Horton
Fibromyalgia
Adenoma
Dental abscess
Rhinoplasty
Fibroma
Chiari malformation
Facial dystonia
Post radiotherapy
Neurofibromatosis
Post COVID-19
Thalamic glioma
Hemangioblastoma
Submaxillary cancer
Cerebral stroke
Osteome
Cranio-facial trauma
Others
0
1
2
3
4
5
6
7
8
9
10
20-29 30-39 40-49 50-59 60-69 70-79 80-89
Femenino
Masculino
Derecho
Izquierdo
Jan 2011-Oct 2021
n= 2210
Epidermoid cysts are slow-growing brain tumors of
embryonic origin that manifest later in life.1
Investigación
Segura

4.  Epidermoid cysts are slow-growing brain
tumors of embryonic origin that manifest
later in life.1
 The anterolateral cisterns of the brainstem
is its most frequent location.2
 They represent approximately 1% of
intracranial tumors.1
 They are present in about 2% of patients
presenting as a first symptom a trigeminal
neuralgia.2
 The study of choice is a high definition MRI
Epidermoid Cyst
(1)Katharine, J. et al. (2012). 14 - Surgical principles in the management of brain tumors, Brain Tumors (Third Edition), W.B. Saunders, 282-295.
(2)Segura-Lozano, MA, et al. (2019) Quiste Epidermoide de las Cisternas Anterolaterales del Tronco Cerebral con Abordaje Subasterional Tipo
Keyhole. Revista Latinoamericana de Neurocirugía/Neurocirurgía, 28(3), 154-176.
Investigación
Segura

5. (1)Katharine, J. et al. (2012). 14 - Surgical principles in the management of brain tumors, Brain Tumors (Third Edition), W.B.
Saunders. 282-295.
Our philosophy on the surgical approach is based
on three principles:
 Preserve the life of the patient.
 Do not damage the nerve and vascular
structures adjacent to the surgical site to
avoid neurological sequelae and
complications inherent to surgery.
 Eliminate the cause of compressive
neuropathy and relieve symptoms
Introduction
Investigación
Segura

6. For this presentation we focus primarily on the anterolateral
location of the brainstem.
Type of approach Extension I Extension II Extension III Total
Retrosigmoid 13 3 1 17 (39.5%)
Lateral Suboccipital 3 7 2 12 (27.9%)
Pterional +Posterior fossa
approach
- 1 6 7 (16.3%)
Subtemporal +Posterior fossa
approach
- - 2 2 (4.7%)
Supra and infratentorial - 2 3 5 (11.6%)
Total 16 13 14 43 (100%)
Revuelta-Gutierrez, R., et al. (2009). "[Cerebellopontine angle epidermoid cysts. Experience of 43 cases with long-term follow-up]." Cir Cir 77(4): 257-265; 241-258.
Relationship between the type of approach used and the degree of extension of
the epidermoid cyst.
Introduction
APC Epidermoid Cyst Extensions:
Type I Limited to the APC in its corresponding extensions.
Type II In addition to the APC cistern, it includes the extension to the perimesencephalic, suprasellar and suprachiasmatic
cisterns.
Type III Extension to the parasellar region and compression of the medial portion of the temporal lobe.
IT
ST

7. 1. Lateral decubitus positioning with head rotation
2. 1 inch skin incision in the retromastoid region
3. Musculoskeletal plane dissection to reach the surface of the
skull
Segura-Lozano, MA, et al. (2019) Quiste Epidermoide de las Cisternas Anterolaterales del Tronco Cerebral con
Abordaje Subasterional Tipo Keyhole. Revista Latinoamericana de Neurocirugía/Neurocirurgía, 28(3), 154-176.
Morbid
obesity
patient
Normal
weight
patient
Our surgical technique in 10 steps
Investigación
Segura

8. 4. Infra-asterional craniectomy <2cm
5. Durotomy in "<" or ">"
6. Depletion of CSF from the posterior fossa
without brain retraction
7. Debulking and tumor resection
8. Treatment of the implant area
9. Hemostatic review of the microsurgical area
10.Hermetic duroplasty and soft tissues
Segura-Lozano, M. A., et al. (2019) Quiste Epidermoide de las Cisternas Anterolaterales del Tronco Cerebral con
Abordaje Subasterional Tipo Keyhole. Revista Latinoamericana de Neurocirugía/Neurocirurgía, 28(3), 154-176.
Our surgical technique in 10 steps

9. Case Surgery date Gender Age Nation
Anesthesia
(min)
Surgery
(min)
Hospital
(days)
Follow-up
(months)
Years of
pain
Affected
side
IT-ST
Extend
Outcome
1 2011-01-13 F 25 US - - - 129 - - ALC Pain
2 2013-01-09 M 35 Mexico - - - 105 - - ALC Good
3 2014-01-01 M 50 Bolivia - - - 93 5 R ALC Good
4 2014-07-22 F 37 Mexico - - - 87 1 R ALC Good
5 2015-09-08 F 32 Mexico 231 210 2 73 2 L ALC Good
6 2015-12-03 M 23 Mexico 239 219 3 70 1 L ALC Good
7 2016-06-05 M 50 US - - - 64 3 L ALC Pain
8 2017-02-03 F 50 Mexico 138 99 3 56 10 R ALC Subt
9 2017-07-24 M 47 Portugal 201 154 2 51 2 R ALC Subt
10 2017-11-14 M 72 Peru 264 217 3 47 1 L ALC Good
11 2018-03-28 F 34 Mexico 215 177 3 43 1 R ALC Good
12 2018-06-08 M 82 Mexico 210 133 4 40 10 R ALC Good
13 2018-06-26 M 21 Bolivia 332 320 4 40 4 R ALC Subt
14 2019-02-18 M 25 Mexico 199 184 3 32 2 L ALC Good
15 2019-03-04 F 42 Mexico 197 170 3 31 10 R ALC Good
16 2019-05-20 F 27 Mexico 181 170 3 29 1 R ALC Good
17 2019-06-04 F 26 Mexico 170 151 3 28 3 R ALC Good
18 2019-07-31 F 39 Mexico 223 180 2 27 1 R ALC Good
19 2020-08-03 F 69 Mexico 209 162 3 14 7 L ALC Good
20 2020-11-12 M 33 Mexico 238 199 3 11 3 R ALC Good
21 2020-01-17 M 48 Mexico 217 185 3 21 2 L ALC Good
22 2020-12-24 F 26 Mexico 233 154 3 10 14 R ALC Good
23 2021-05-25 F 58 Mexico 217 173 3 5 12 L ALC Good
24 2021-06-21 M 45 Mexico 207 188 3 4 3 L ALC Good
25 2021-06-24 F 52 US 161 131 3 4 20 L ALC Good
26 2021-08-23 F 38 Mexico 203 164 3 2 12 R ALC Good
F= 14 Prom:
43
Nat: 25 Prom:
213
Prom:
178
Prom:
2.9
Prom:
36
Prom:
5.4
R = 58% ALC=
100%
Good:
87,5%
M= 12 Foreign: 8 L = 42%
Anterolateral brainstem cisterns (infratentorial)
ALC = Anterolateral Cisterns
Investigación
Segura

10. Case 1. Complete resection

11. Preoperative (A) and postoperative (B) MRI (3D-FIESTA) with axial section at the level of the bridge
of a patient with total resection
………..

12. Case 2. Complete resection with residual implant

13. Preoperative (A) and postoperative (B) MRI (3D-FIESTA) with axial section at the level of the
bridge of a patient with subtotal resection
flóculo

15. Resultados:

16. Preoperative (A) and postoperative (B) MRI with coronal section of a
case of epidermoid cyst with supratentorial extension

17. Juana Case 4. Complete resection with lateral ST residual tumor

18. Preoperative (A) and postoperative (B) MRI (3D-FIESTA) with coronal section of a
case of epidermoid cyst with medial and lateral supratentorial extension

19. Case 5. First stage resection with lateral and medial ST
residual tumor

20. Preoperative (A) and postoperative (B) MRI (3D-FIESTA) with coronal section of
a case of epidermoid cyst with medial and lateral supratentorial extension

21. Our series of EC cases in the ALCs of the brainstem is one of the largest published in
Latin America and, based on the excellent long-term results obtained, we propose this
minimally invasive microsurgical approach as the best treatment.
Comprehensive anterolateral cisterns of the brainstem as a 3D space concept
Non-septate but monocompartmental, non-infiltrative towards the adjacent arachnoid
Complete or subtotal excision without implant zone is the goal in the first surgery
Due to the rarity of the entity, we recommend that the neurosurgeon interested in
treating this type of tumor be trained in laboratories with cadavers, with software for
3D virtual surgery and under the tutelage of an expert neurosurgeon to resolve
contingencies that may arise during the curve learning.
Conclusions
Investigación
Segura