This document discusses foramen magnum meningiomas, a type of brain tumor. It defines the foramen magnum region and describes the structures that pass through it. Foramen magnum meningiomas present with variable neurological symptoms and are challenging to treat due to their proximity to critical structures. Imaging plays an important role in diagnosis and surgical planning. The surgical approach depends on factors such as tumor location and relationship to the vertebral artery. Complications can include lower cranial nerve deficits, cerebrospinal fluid leakage, and vascular injury. Complete resection remains the goal but must be balanced against risk of morbidity.

1. cka
Dr. Suresh Bishokama, MS
MCH Neurosurgery ®
Department of Neurosurgery, Upendra Devkota Memorial National Institute of
Neurological and Allied Sciences
Bansbari, Kathmandu
FORAMEN MAGNUM MENINGIOMA

2.  A meningioma is considered to be located into the FM
region if its insertion zone is mainly situated into the FM
area.
 FM area is defined by these landmarks
1. Anterior border: lower third of the clivus and upper edge
of the body of C2
2. Lateral borders: jugular tubercles and upper aspect of C2
laminas
3. Posterior border: anterior edge of the squamous occipital
bone and C2 spinous process
 STRUCTURE PASSING VIA FM:
Limits of the FM
2 PICA, 3 CN XII, 4
vertebral artery V4
segment, 5 C1, 6
dentate ligament, 7: VA3
1. Medulla oblongata
2. Ascending part of spinal accessory n.
3. Vertebral artery

3.  Foramen magnum meningiomas are challenging tumors, requiring special considerations
because of the vicinity of the medulla oblongata, the lower cranial nerves, and the vertebral
artery.
 Meningiomas represent 25 – 30 % of all hospital-based primary intracranial neoplasms.
The foramen magnum meningiomas constitutes 1 – 3 % of all cranial meningiomas.
FORAMEN MAGNUM MENINGIOMAS

4. Variable symptoms.
 The lesion is often large when discovered because of their slow-growing rate, their indolent
development, the difficulty of the diagnosis leading to a long interval since the first symptom, and
the wide subarachnoid space at this level.
 Neck or sub-occipital pain exacerbated by coughing, straining, or sneezing.
 Motor sensory symptoms develop, usually in one arm, and then in the contralateral leg. (Elsberg
phenomenon)
 Gait disturbances, diplopia, dysphagia, dysarthria, dyspnea, sphincter disturbances, vomiting,
nausea are some of the common symptoms.
 The most common neurological sign is hyperreflexia, followed by weakness of the extremities in
all combinations (hemiparesis/plegia, quadriparesis/plegia) and sensory loss.
 The Babinski sign, a gait disturbances, or lower CN (IX-XI) palsies are present in approximately
half of patients with this tumor.
 CN XI is most commonly affected, presented by the shoulder weakness because of atrophy of
sternocleidomastoids and trapezius muscles.
 Dissociated sensory loss, loss of coordination in the hands, Brown-Sequard syndrome, down-
beating nystagmus, and nuchal rigidity and tenderness occur in one quarter to one third of
patients.
 Papilledema, Horner’s syndrome, and dysarthria are less common neurological findings.
 Because of the lower cranial nerve morbidity associated with surgical resection of these tumors,
incidentally discovered tumors in this location can initially be followed.
CLINICAL PRESENTATION

5. 1. Anteriorly from the inferior third of the clivus to the superior edge of the C2 body.
2. Laterally from the jugular tubercle to the C2 laminae
3. Posteriorly from the anterior border of the occipital squama to the spinal process of C2.
Origin of FMM

6. The neural elements:
1. Inferior vermis,
2. Cerebellar tonsils,
3. Fourth ventricle,
4. Lower cranial nerves from 9 – 12th,
5. Caudal aspect of the medulla oblongata
6. Rostral aspect of the spinal cord and
7. Upper cervical nerves C1 and C2.
Important neurovascular structures
The vascular structures:
1.Vertebral arteries,
2.Posterior inferior cerebellar arteries,
3.The meningeal branches of the vertebral
artery,
4.The posterior and anterior spinal arteries
and
5.The venous plexus.

7.  Classification of foramen magnum meningiomas (FMM) depending on:
1. Their compartment of development:
i. Intradural (most commonly),
ii. Extradural (invasive into the bone, nerves and vessels sheaths)
iii. Intra-extradural.
2. Their dural insertion:
i. Anterior :Insertion on both side of the anterior mdiiline
ii. Posterior : Insertion posterior to the dentate ligaments
iii. Posterolateral : Insertion between midline and the dentate ligament
iv. Anterolateral:
3. Their relation to the VAs:
i. Above (the position of the lower cranial nerves cannot be anticipated),
ii. Below (the lower cranial nerves are pushed cranially and posteriorly) and
iii. On both sides
Classification
Boulton MR, Cusimano MD, Foramen magnum meningiomas: concepts, classifications and nuance. Neurosurg Focus 14, 2003

8. Classification
Bruneau M and George B

9.  The role of neuroimaging is to confirm the clinical diagnosis and to allow the planning of a
surgical approach.
 Magnetic resonance imaging is the modality of choice for defining tumors of the foramen
magnum.
 CT scan: Bony erosions and hyperstosis.
Imaging

10.  With meninigoma below VA, The lower CNs are displaced superiorly while
 Tumor above VA, the position is unpredictable.
Relationship of VA with meningioma

11. Conventional angiography is generally useless.
There are only two indications for preoperative angiography:
1. If a highly vascularized tumor is suspected and embolization is contemplated
2. To perform a balloon occlusion test in case of VA encasement (extradural or
recurrent meningioma and meningioma inserted around the VA).
Conventional angiography

12. CONSIDERATION
1. The location of the tumor
2. The extent of the tumor (above the foramen magnum)
3. The relation of the tumor with the vertebral artery and with the origin of posterior inferior
cerebellar artery
4. Choice of the surgical approach,
5. Extent of bone resection
6. Management of the vertebral artery (VA) and
7. Involvement of lower cranial nerves (CN)
SURGICALAPPROACH

13. NORMAL RELATIONSHIP OF BRAINSTEM AND
TUMOR TO FORAMEN MAGNUM
A: Normal relationship of brainstem to foramen magnum. OC = occipital condyle; CMJ = cervicomedullary junction. B-D: As the
tumor (T) enlarges, it displaces the brainstem posteriorly and typically to one side, naturally creating a widened surgical corridor. B:
A narrow corridor of less than 1 cm between the condyle and cervicomedullary junction. C: Adequate corridor with a 1-2 cm
distance. D: Large corridor (> 2 cm) that allows relatively easy access to the anterior foramen magnum. (2

14. SURGICAL APPROACHES OF FORAMEN MAGNUM
Posterior (for intradural lesions), lateral (intradural lesion situated lateral to
and / or in front of the brainstem), anterior (for extradural lesions)

15.  The midline posterior approach
 Posterior meningiomas (intra- and extradural extension): posterior to the plane of the
dentate ligament and medial to the VA.
 Postero-lateral approach
 Intradural process located laterally and/or anteriorly to the neuraxis
 Extradural lesions developed on the posterior part of the lateral FM wall.
 Antero-lateral approach
 Rarely used
 Meningiomas with extradural extension through the bony structures
SURGICALAPPROACHES

16. THE FAR-LATERALAPPROACH TO FMMS.

17. 1. Temporary:
 CSF leak
 Pseudomeningocele
 Lower cranial nerve deficits (IX–XII)
 Air embolism
 Hemiparesis
 Postop epidural hematoma
 Wound infection
 Meningitis
 Need for tracheostomy/gastrostomy
2. Permanent
 Lower cranial nerve deficits (IX–XII) hydrocephalus
 VA injury
 Tetraplegia
 Need for tracheostomy/gastrostomy
Morbidity with Far lateral surgery

18.  The transoral approach: did not acquired great acceptance: Risks
 Cerebrospinal fluid leak and
 Meningitis, difficult access for tumors with lateral extension and
 Risk of postoperative craniocervical instability and
 Velopalatine insufficiency
 The far-lateral and the extreme-lateral approaches are the most utilized nowadays.
 In both approaches it is possible to remove partially the occipital condyle but they provide
different exposure because of different angles of approaches to the anterior FM.
 The extreme-lateral approach requires VA transposition for drilling the occipital condyle
SURGICALAPPROACHES

19. SURGICAL APPROACH TO AN ANTERIOR FORAMEN MAGNUM
MENINGOMA
A: Suboccipital craniotomy (red) with a narrow corridor does not provide adequate exposure of the tumor for resection.
B: Tumor growth naturally widens the surgical corridor, allowing its safe and effective removal via suboccipital craniotomy without
drilling of the condyle.
C: Transcondylar exposure (blue) widens the corridor by removing the medial condyle (red arrow represents very narrow corridor before
excision of the condyle, green arrow
represents adequate corridor after this resection).
D.Access to much of the tumor has been created

20. 1. Anterior location: Difficult
2. Tumor size (bigger lesions are easier to be resected)
3. Tumor invasiveness
4. Extradural extension
5. VA encasement
6. Absence of arachnoidal layer
7. Adherences in recurrent lesions.
Prognostic factors

21. 1. Yasargil 1976: Morbidity: ~13% ( Others: 45%)
2. Lower CN deficits: Sharp dissection of the arachnoid plane is key to
preserving the rootlets of cranial nerves IX, X, XI, and XII.
3. Hemiparesis, tetraparesis,
4. Sensory deficits,
5. Hydrocephalus,
6. Craniospinal fluid leak, meningitis and
7. General complications as pneumonia, and respiratory faiuure.
Outcome of surgery

22. Thank you

NATIONAL INSTITUTE OF NEUROLOGICAL AND ALLIED SCIENCES, BANSBARI, KATHMANDU
FORAMEN MAGNUM MENINGIOMA
UPENDRA DEVKOTA MEMORIAL NATIONAL INSTITUTE OF NEUROLOGICALAND ALLIED SCIENCES,
BANSBARI, KATHMANDU