Endoscopic endonasal surgery is a minimally invasive technique used mainly in

neurosurgery Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and pe ...

and

otolaryngology Otorhinolaryngology ( , abbreviated ORL and also known as otolaryngology, otolaryngology–head and neck surgery (ORL–H&N or OHNS), or ear, nose, and throat (ENT)) is a surgical subspeciality within medicine that deals with the surgical a ...

. A neurosurgeon or an otolaryngologist, using an

endoscope An endoscope is an inspection instrument composed of image sensor, optical lens, light source and mechanical device, which is used to look deep into the body by way of openings such as the mouth or anus. A typical endoscope applies several modern t ...

that is entered through the nose, fixes or removes brain defects or tumors in the anterior skull base. Normally an otolaryngologist performs the initial stage of surgery through the

nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal ...

and

sphenoid bone The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the o ...

; a neurosurgeon performs the rest of the surgery involving drilling into any cavities containing a neural organ such as the

pituitary gland In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The h ...

. The use of endoscope was first introduced in Transsphenoidal Pituitary Surgery by R Jankowsky, J Auque, C Simon et al. in 1992 G (Laryngoscope. 1992 Feb;102(2):198-202).

Introduction

History of endoscopic endonasal surgery

Antonin Jean Desomeaux, a urologist from Paris, was the first person to use the term, endoscope. However, the precursor to the modern endoscope was invented in the 1800s when a physician in Frankfurt, Germany by the name of

Philipp Bozzini Philipp Bozzini (May 25, 1773 – April 4, 1809) was born in Mainz, Germany. On June 12, 1797 he was awarded the degree of doctor of medicine. From 1804 onwards, Bozzini devoted himself virtually completely to develop his instrument, Lichtleiter ...

, developed a tool to see the inner workings of the body. Bozzini called his invention a Light Conductor, or Lichtleiter in German, and later wrote about his experiments on live patients with this device that consisted of an eyepiece and a container for a candle. Following Bozzini's success, The University of Vienna starting using the device to test its practicality in other forms of medicine. After Bozzini's device received negative results from live human trials, it had to be discontinued. However, Maximilian Nitze and Joseph Leiter used the invention of the light bulb by Thomas Edison to make a more refined device similar to modern day endoscopes. This iteration was used for urological procedures, and eventually otolaryngologists began to use Nitze and Leiter's device for

eustachian tube In anatomy, the Eustachian tube, also known as the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately long and in d ...

manipulation and removal of foreign bodies. The endoscope made its way to the US when Walter Messerklinger began teaching David Kennedy at Johns Hopkins Hospital. The transsphenoidal and intracranial approaches to pituitary tumors began in the 1800s but with little success. Gerard Guiot popularized the transphenoidal approach which later became part of the neurosurgical curriculum, however he himself discontinued the use of this technique because of inadequate sight. In the late 1970s, the endoscopic endonasal approach was used by neurosurgeons to augment microsurgery which allowed them to view objects out of their line of sight. Another surgeon, Axel Perneczky, is considered to be a pioneer of the use of an endoscope in neurosurgery. Perneczky said that endoscopy, "improved appreciation of micro-anatomy not apparent with the microscope." The surgery was pioneered in Algeria by Bouyoucef Kheireddine and

Faiza Lalam Faiza Lalam ( ar, فايزة لعلام) is a medical doctor from Algeria, who is credited as the first woman neurosurgeon in Africa, spearheading the work of women in the specialism on the continent. She was described in 2020 as the "'Dean' of wo ...

Endoscopic instrumentation

The endoscope consists of a glass fiber bundle for cold light illumination, a mechanical housing, and an optics component with four different views: 0 degree for straight forward, 30 degrees for forward plane, 90 degrees for lateral view, and 120 degrees for retrospective view. For endoscopic endonasal surgery, rigid rod-lens endoscopes are used for better quality of vision, since these endoscopes are smaller than the normal endoscope used

colonoscopies Colonoscopy () or coloscopy () is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis (''e.g ...

. The endoscope has an eyepiece for the surgeon, but it is rarely used because it requires the surgeon to be in a fixed position. Instead, a video camera broadcasts the image to a monitor that shows the surgical field.

Areas of interest for surgical planning

Several specialties need to be involved to determine the complete surgical plan. These include: an Endocrinologist, a Neuroradiologist, an Ophthalmologist, a Neurosurgeon, and an Otolaryngologist.

Endocrinology

An endocrinologist is only involved in preparation for an endoscopic endonasal surgery, if the tumor is located on the pituitary gland. The tumor is first treated pharmacologically in two ways: controlling the levels of

hormone A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...

s that the

secretes and reducing the size of the tumor. If this approach does not work, the patient is referred to surgery. The main types of

pituitary adenomas Pituitary adenomas are tumors that occur in the pituitary gland. Most pituitary tumors are benign, approximately 35% are invasive and just 0.1% to 0.2% are carcinomas.prolactinomas: These are the most common pituitary tumors. They are associated with

infertility Infertility is the inability of a person, animal or plant to reproduce by natural means. It is usually not the natural state of a healthy adult, except notably among certain eusocial species (mostly haplodiploid insects). It is the normal st ...

gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sp ...

, and

sexual dysfunction Sexual dysfunction is difficulty experienced by an individual or partners during any stage of normal sexual activity, including physical pleasure, desire, preference, arousal, or orgasm. The World Health Organization defines sexual dysfunction a ...

because they increase the secretion of

prolactin Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the pi ...

or PRL. One drug that endocrinologist use is

bromocriptine Bromocriptine, originally marketed as Parlodel and subsequently under many brand names, is an ergoline derivative and dopamine agonist that is used in the treatment of pituitary tumors, Parkinson's disease, hyperprolactinaemia, neuroleptic ...

(BRC), which normalizes PRL levels and has been shown to lead to tumor shrinkage. Other drugs to treat prolactinomas include quinagolide (CV) or cabergoline (CAB) acting as

dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. Dopamine constitutes about 80% o ...

(D2) antagonists. Endoscopic endonasal surgery is normally performed as a last resort when the tumor is resistant to the drugs, shows no tumor shrinkage, or the PRL levels cannot be normalized. * GH-secreting: A very rare condition that is a result of the increase in the secretion of

growth hormone Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in ...

. There are currently less than 400,000 cases worldwide and approximately 30,000 new cases every year. Despite the rarity of this condition, these tumors constitute 16% of the pituitary tumors that are removed. The tumor normally results in acral enlargement,

arthropathy An arthropathy is a disease of a joint. Types Arthritis is a form of arthropathy that involves inflammation of one or more joints, while the term arthropathy may be used regardless of whether there is inflammation or not. Joint diseases can be ...

hyperhidrosis Hyperhidrosis is a condition characterized by abnormally increased sweating, in excess of that required for regulation of body temperature. Although primarily a benign physical burden, hyperhidrosis can deteriorate quality of life from a psychologi ...

, changes in facial features,

soft tissue Soft tissue is all the tissue in the body that is not hardened by the processes of ossification or calcification such as bones and teeth. Soft tissue connects, surrounds or supports internal organs and bones, and includes muscle, tendons, ...

swelling,

headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result ...

s, visual changes, or

hypopituitarism Hypopituitarism is the decreased (''hypo'') secretion of one or more of the eight hormones normally produced by the pituitary gland at the base of the brain. If there is decreased secretion of one specific pituitary hormone, the condition is know ...

. Since pharmacological therapy has had little effect on these tumors, a trans-sphenoidal surgery to remove part of the pituitary gland is the first treatment option. * TSH-secreting: Another rare condition only resulting in 1% of pituitary surgeries is a result of the increase in the secretion of the

thyroid-stimulating hormone Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3) which stimulates the metabolism ...

. This tumor leads to

hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidis ...

, resulting in headaches and visual disturbances. Although surgery is the first step of treatment, it does not usually cure the patient. After surgery, patients are treated by

somatostatin Somatostatin, also known as growth hormone-inhibiting hormone (GHIH) or by several other names, is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein-cou ...

analogues, a type of

hormone replacement therapy Hormone replacement therapy (HRT), also known as menopausal hormone therapy or postmenopausal hormone therapy, is a form of hormone therapy used to treat symptoms associated with female menopause. These symptoms can include hot flashes, vaginal ...

, because TSH related tumors increase the expression of somatostatin receptors. * ACTH-secreting: This tumor is a result of the increase in the secretion of

adrenocorticotropic hormone Adrenocorticotropic hormone (ACTH; also adrenocorticotropin, corticotropin) is a polypeptide tropic hormone produced by and secreted by the anterior pituitary gland. It is also used as a medication and diagnostic agent. ACTH is an important c ...

(ACTH) and leads to

Cushing's syndrome Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, a ...

. Pharmacology has little effect and therefore surgery is the best option. Removal of the tumor results in an 80%-90% cure rate.

Neuroradiology

A neuroradiologist takes images of the defect so that the surgeon is prepared on what to expect before surgery. This includes identifying the

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classif ...

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

, controlling the effects of the medical therapy, defining the spatial situation of the lesions, and verifying the removal of the lesions. The lesions associated with endoscopic endonasal surgery include: * Pituitary microadenomas * Pituitary macroadenomas *

Rathke's cleft cyst A Rathke's cleft cyst is a benign growth on the pituitary gland in the brain, specifically a mucin-filled cyst in the posterior portion of the anterior pituitary gland. It occurs when the Rathke's pouch does not develop properly and ranges in si ...

s * Pituitary inflammatory disease * Pituitary

metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, the ...

* Empty Sella *

Craniopharyngioma A craniopharyngioma is a rare type of brain tumor derived from pituitary gland embryonic tissue that occurs most commonly in children, but also affects adults. It may present at any age, even in the prenatal and neonatal periods, but peak incidence ...

s * Meningiomas * Chiasmatic and Hypothalamic

glioma A glioma is a type of tumor that starts in the glial cells of the brain or the spine. Gliomas comprise about 30 percent of all brain tumors and central nervous system tumours, and 80 percent of all malignant brain tumours. Signs and symptoms ...

s * Germinomas * Tuber Cinereum Hamartomas *

Arachnoid cyst Arachnoid cysts are cerebrospinal fluid covered by arachnoidal cells and collagen that may develop between the surface of the brain and the cranial base or on the arachnoid membrane, one of the three meningeal layers that cover the brain and the ...

s * Neurinomas of the trigeminal nerve

Ophthalmology

Some suprasellar tumors invade the chiasmatic cistern, causing impaired vision. In these cases, an ophthalmologist maintains optic health by administering pre-surgical treatment, advising proper surgical techniques so that the optic nerve is not in danger, and managing post-surgery eye care. Common problems include: * Visual field defects * Reduced visual activity * Visually evoked potential (VEP) abnormalities *

Color blindness Color blindness or color vision deficiency (CVD) is the decreased ability to see color or differences in color. It can impair tasks such as selecting ripe fruit, choosing clothing, and reading traffic lights. Color blindness may make some aca ...

* Eye

motility Motility is the ability of an organism to move independently, using metabolic energy. Definitions Motility, the ability of an organism to move independently, using metabolic energy, can be contrasted with sessility, the state of organisms th ...

impairment

Surgical approaches to the anterior skull base

Transnasal approach

The transnasal approach is used when the surgeon needs to access the roof of the nasal cavity, the clivus, or the odontoid. This approach is used to remove

chordoma Chordoma is a rare slow-growing neoplasm thought to arise from cellular remnants of the notochord. The evidence for this is the location of the tumors (along the neuraxis), the similar immunohistochemical staining patterns, and the demonstration ...

chondrosarcoma Chondrosarcoma is a bone sarcoma, a primary cancer composed of cells derived from transformed cells that produce cartilage. A chondrosarcoma is a member of a category of tumors of bone and soft tissue known as sarcomas. About 30% of bone sarcomas ...

, inflammatory lesions of the clivus, or

in the cervical spine region. The anterior

septum In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interat ...

or posterior septum is removed so that the surgeon can use both sides of the nose. One side can be used for a microscope and the other side for a surgical instrument, or both sides can be used for surgical instruments.

Transsphenoidal approach

This approach is the most common and useful technique of endoscopic endonasal surgery and was first described in 1910 concurrently by

Harvey Cushing Harvey Williams Cushing (April 8, 1869 – October 7, 1939) was an American neurosurgeon, pathologist, writer, and draftsman. A pioneer of brain surgery, he was the first exclusive neurosurgeon and the first person to describe Cushing's disease ...

and Oskar Hirsch. This procedure allows the surgeon to access the sellar space, or

sella turcica The sella turcica ( Latin for 'Turkish saddle') is a saddle-shaped depression in the body of the sphenoid bone of the human skull and of the skulls of other hominids including chimpanzees, gorillas and orangutans. It serves as a cephalometr ...

. The sella is a cradle where the pituitary gland sits. Under normal circumstances, a surgeon would use this approach on a patient with a pituitary adenoma. The surgeon starts with the transnasal approach prior to using the transsphenoidal approach. This allows access to the sphenoid ostium and sphenoid sinus. The sphenoid ostium is located on the anterosuperior surface of the sphenoid sinus. The anterior wall of the sphenoid sinus and the sphenoid rostrum is then removed to allow the surgeon a panoramic view of the surgical area. This procedure also requires the removal of the posterior

to allow the use of both nostrils for tools during surgery. There are several triangles of blood vessels traversing this region, which are just very delicate areas of blood vessels that can be deadly if injured. A surgeon uses stereotactic imaging and a micro Doppler to visualize the surgical field. The invention of the angled endoscope is used to go beyond the sella to the suprasellar (above the sellar) region. This is done with the addition of four approaches. First the transtuberculum and transplanum approaches are used to reach the suprasellar

cistern A cistern (Middle English ', from Latin ', from ', "box", from Greek ', "basket") is a waterproof receptacle for holding liquids, usually water. Cisterns are often built to catch and store rainwater. Cisterns are distinguished from wells by ...

. The lateral approach is then used to reach the medial

cavernous sinus The cavernous sinus within the human head is one of the dural venous sinuses creating a cavity called the lateral sellar compartment bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica. Structure The cave ...

and petrous apex. Lastly, the inferior approach is used to reach the superior clivus. Endoscopic endonasal transclival approaches are often described according to which segment of the clivus is involved in the approach, with the clivus typically divided into three regions. Depending on which segment of the clivus is involved in the surgical approach, different neurovascular structures are placed at risk. The upper third lies inferior to the dorsum sellae and posterior clinoid processes and superior to the petrous apex, the middle third lies at the level of the petrous segments of the internal carotid artery (ICA), and the inferior third extends from the jugular tubercle to the foramen magnum. It is important that the Perneczky triangle is treated carefully. This triangle has optic nerves, cerebral arteries, the third cranial nerve, and the pituitary stalk. Damage to any of these could provide a devastating post-surgical outcome.

Transpterygoidal approach

The transpterygoidal approach enters through the posterior edge of the

maxillary sinus The pyramid-shaped maxillary sinus (or antrum of Highmore) is the largest of the paranasal sinuses, and drains into the middle meatus of the nose through the osteomeatal complex.Human Anatomy, Jacobs, Elsevier, 2008, page 209-210 Structure It i ...

ostium and posterior wall of the maxillary sinus. This involves penetrating three separate sinus cavities: the ethmoid sinus, the

sphenoidal sinus The sphenoid sinus is a paired paranasal sinus occurring within the within the body of the sphenoid bone. It represents one pair of the four paired paranasal sinuses.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012 ...

, and the maxillary sinus. Surgeons use this method to reach the

, lateral

sphenoid sinus The sphenoid sinus is a paired paranasal sinus occurring within the within the body of the sphenoid bone. It represents one pair of the four paired paranasal sinuses.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012 ...

, infra

temporal fossa The temporal fossa is a fossa (shallow depression) on the side of the skull bounded by the temporal lines and terminating below the level of the zygomatic arch. Boundaries * Medial: frontal bone, parietal bone, temporal bone, and sphenoid bon ...

, pterygoid fossa, and the petrous apex. Surgery includes a uninectomy (removal of the osteomeatal complex), a medial maxillectomy (removal of maxilla), an ethmoidectomy (removal of ethmoid cells and/or ethmoid bone), a sphenoidectomy (removal of part of sphenoid), and removal of the maxillary sinus and the palatine bone. The posterior septum is also removed at the beginning to allow use of both nostrils.

Transethmoidal approach

This approach makes a surgical corridor from the

frontal sinus The frontal sinuses are one of the four pairs of paranasal sinuses that are situated behind the brow ridges. Sinuses are mucosa-lined airspaces within the bones of the face and skull. Each opens into the anterior part of the corresponding middle ...

to the

. This is done by the complete removal of the

ethmoid The ethmoid bone (; from grc, ἡθμός, hēthmós, sieve) is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a ...

bone, which allows a surgeon to expose the roof of the ethmoid, and the medial orbital wall. This procedure is often successful in the removal of small encephaloceles of the ethmoid osteomas of the ethmoid sinus wall or small

olfactory The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...

groove

meningioma Meningioma, also known as meningeal tumor, is typically a slow-growing tumor that forms from the meninges, the membranous layers surrounding the brain and spinal cord. Symptoms depend on the location and occur as a result of the tumor pressing ...

s. However, with larger tumors or lesions, one of the other approaches listed above is required.

Different approaches to specific regions

Approach to sellar region

For removal of a small tumor, it is accessed through one nostril. However, for larger tumors, access through both nostrils is required and the posterior nasal

must be removed. Then the surgeon slides the endoscope into the nasal

choana The choanae (singular choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the throat in tetrapods, including humans and other mammals (as well as crocodili ...

until the sphenoid ostium is found. Then the mucosa around the ostium is cauterized for microadenomas and removed completely for macroadenomas. Then the endoscope enters the ostium and meets the sphenoid rostrum where the

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...

is retracted from this structure and is removed from the

to open the surgical pathway. At this point, imaging and Doppler devices are used to define the important structures. Then the floor of the

is opened with a high speed drill being careful to not pierce the

dura mater In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. ...

. Once the dura is visible, it is cut with microscissors for precision. If the tumor is small, the tumor can be removed by an ''en bloc'' procedure, which consists of cutting the tumor into many sections for removal. If the tumor is larger, the center of the tumor is removed first, then the back, then the sides, then top of the tumor to make sure that the arachnoid membrane does not expand into the surgical view. This will happen if the top part of the tumor is taken out too early. After tumor removal, CSF leaks are tested for with fluorescent dye, and if there are no leaks, the patient is closed.

Approach to suprasellar region

This technique is the same as to the sellar region. However the

tuberculum sellae The tuberculum sellae (or the tubercle of the sella turcica) is a part of the sphenoid bone that is an elevation behind the chiasmatic groove The superior surface of the body of the sphenoid bone is bounded behind by a ridge, which forms the ante ...

is drilled into instead of the sella. Then an opening is made that extends halfway down the sella to expose the dura, and the intercavernous sinuses is exposed. When the

optic chiasm In neuroanatomy, the optic chiasm, or optic chiasma (; , ), is the part of the brain where the optic nerves cross. It is located at the bottom of the brain immediately inferior to the hypothalamus. The optic chiasm is found in all vertebrat ...

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived fro ...

, and

are visible, the pituitary gland and optic chasm are pushed apart to see the pituitary stalk. An ethmoidectomy is performed, the dura is then cut, and the tumor is removed. These types of tumors are separated into two types: * Prechiasmal Lesions: This tumor is closest to the dura. The tumor is decompressed by the surgeon. After decompression, the tumor is removed taking care to not disrupt any optic nerve or major arteries. * Postchiasmal Lesions: This time the pituitary stalk is in the front because the tumor is pushing it towards the area the dura was opened. Removal then starts on both sides of the stalk to preserve the connection between the pituitary and the

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus ...

and above pituitary gland to protect the stalk. The tumor is carefully removed and the patient is closed up.

Skull base reconstruction

When there is a tumor, injury, or some type of defect at the skull base whether the surgeon used an endoscopic or open surgical method, the problem still arises of providing separation of the

cranial cavity The cranial cavity, also known as intracranial space, is the space within the skull that accommodates the brain. The skull minus the mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the hu ...

and cavity between the sinuses and nose to prevent

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...

leakage through the opening referred to as a defect. For this procedure, there are two ways to start: with a free graft repair or with a vascularized flap repair. The free grafts use secondary material like

cadaver A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Stud ...

flaps or titanium mesh to repair the skull base defects, which is very successful (95% without CSF leaks) with small CSF fistulas or small defects. The local or regional vascularized flaps are pieces of tissue relatively close to the surgery site that have been mostly freed up but are still attached to the original tissue. These flaps are then stretched or maneuvered onto the desired location. When technology advanced and larger defects could be fixed endoscopically, more and more failures and leaks started to occur with the free graft technique. The larger defects are associated with a wider dural removal and an exposure to high flow CSF, which could be the reason for failure among the free graft.

Pituitary gland surgery

This surgery is turned from a very serious surgery into a minimally invasive one through the nose with the use of the endoscope. For instance

craniopharyngioma A craniopharyngioma is a rare type of brain tumor derived from pituitary gland embryonic tissue that occurs most commonly in children, but also affects adults. It may present at any age, even in the prenatal and neonatal periods, but peak incidence ...

s (CRAs) are starting to be removed via this method. Dr. Paolo Cappabianca described the perfect CRA for this surgery to be a median lesion with a solid parasellar component (beside the sellar) or encasement of the main neuromuscular structures that are localized in the subchiasmatic (below the

) and retrochiasmatic (behind the optic chiasm) regions. He also says that when these conditions are met, endoscopic endonasal surgery is a valid surgical option. For a case study on large adenomas, the doctors showed that out of 50 patients, 19 had complete tumor removal, 9 had near complete removal, and 22 had partial removal. The partial removal came from the tumors extending into more dangerous areas. They concluded that endoscopic endonasal surgery was a valid option for surgery if the patients used pharmacological therapy after surgery. Another study showed that with endoscopic endonasal surgery 90% of microadenomas could be removed, and that 2/3 of normal macroadenomas could be removed if they did not go into the

, which means fragile blood vessel triangles would have to be dealt with so only 1/3 of those patients recovered. Endoscopic endonasal approach has been shown even among young patients to be superior to traditional microscopic transsphenoidal surgery.

3-D approach vs 2-D approach

The newer 3-D technique is gaining ground as the ideal way to do surgery because it gives the surgeon a better understanding of the spatial configuration of what they are seeing on a computer screen. Dr. Nelson Oyesiku at Emory University helped develop the 3-D technique. In an article he helped write, he and the other authors compared the effects of the 2-D technique vs the 3-D technique on patient outcome. It showed that the 3-D endoscopy gave the surgeon more depth of field and stereoscopic vision and that the new technique did not show any significant changes in patient outcomes during or after surgery.

Endoscopic techniques vs open techniques

In a case study from 2013, they compared the open vs endoscopic techniques for 162 other studies that contained 5,701 patients. They only looked at four tumor types: the olfactory groove

s (OGM), tuberculum sellae meningiomas (TSM),

craniopharyngiomas A craniopharyngioma is a rare type of brain tumor derived from pituitary gland embryonic tissue that occurs most commonly in children, but also affects adults. It may present at any age, even in the prenatal and neonatal periods, but peak incidenc ...

(CRA), and clival

s (CHO). They looked at gross total resection and

(CSF) leaks, neurological death, post-operative visual function, post operative

diabetes insipidus Diabetes insipidus (DI), recently renamed to Arginine Vasopressin Deficiency (AVP-D) and Arginine Vasopressin Resistance (AVP-R), is a condition characterized by large amounts of dilute urine and increased thirst. The amount of urine produced ...

, and post-operative obesity. The study showed that there was a greater chance of CSF leaks with endoscopic endonasal surgery. The visual function improved more with endoscopic surgery for TSM, CRA, and CHO patients. Diabetes insipidus occurred more in open procedure patients. The endoscopic patients showed a higher recurrence rate. In another case study on CRAs, they showed similar results with the CSF leaks being more of a problem in endoscopic patients. Open procedure patients showed a higher rate of post operative seizures as well. Both of these studies still suggest that despite the CSF leaks, that the endoscopic technique is still an appropriate and suitable surgical option. Otologic surgery, which is traditionally performed via an open approach using a microscope, may also be performed endoscopically, and is called Endoscopic Ear Surgery or EES.

References

{{reflist Endocrine surgery Endoscopy Neurosurgery Surgical procedures and techniques