Meninges the Cibirio

𝙲𝚛𝚎𝚊𝚝𝚞𝚛𝚎 𝙿𝚛𝚘𝚏𝚒𝚕𝚎: 𝙼𝚎𝚗𝚒𝚗𝚐𝚎𝚜




𝑨𝒃𝒐𝒖𝒕 𝑴𝒆𝒏𝒊𝒏𝒈𝒆𝒔

The nervous system is personally the most complex out of the body systems.
Let's learn a bit about brain anatomy!
(these are all based on what I can remember on my neuro notes)

The meninges are protective layers that envelop both the brain and the spinal cord. Their primary role is to provide structural support for cerebrovasculature + prevents mechanical damage to the soft tissues of the brain. Pathologies of this structure include meningitis & intracranial hemorrhage. It comprises of three layers:

Dura Mater
- consists of 2 layers:
Periosteal - lines the cranium
Meningeal - the deeper layer, continuous with the spinal cord's dura mater
- important structure: Dural venous sinus - cranial venous drainage -> to the IJV
- blood supply: Middle meningeal A & V
- Dural reflections = the meningeal layer folds upon itself & form 4 reflections:
1. falx cerebri - separates the brain into 2 hemispheres
2. falx cerebelli - separates the cerebellum into 2 hemispheres
3. tentorium cerebelli - separates the occipital lobes from the cerebellum;
has a tentorial notch for the midbrain to pass anteromedially
4. diaphragma sella - lines the hypophyseal fossa of the sphenoid bone where you can find the pituitary gland

Arachnoid Mater
- middle layer, avascular
- has tiny projections into the dura mater called arachnoid granulations that allow CSF to be recirculated via the dura venous sinus
- has a space below it called the subarachnoid space that contains CSF that acts as the brain's cushion

Pia Mater
- innermost layer, highly vascular
- very thin & adherent to the brain & spinal cord surfaces
- provides nourishment to underlying neural tissue

𝑴𝒆𝒏𝒊𝒏𝒈𝒊𝒐𝒎𝒂

Meningiomas are the most common primary brain tumor, accounting for ~35% of the total.
Molecular defect in most cases: somatic loss-of-function mutations in the NF2 tumor suppressor gene on the long arm of chromosome 22 (22q)
Risk factors: older age, female, neurofibromatosis type 2 (NF2), history of cranial irradiation.
Tumors origin: arachnoid meningothelial cells

Possible locations: cerebral convexities (near the sagittal sinus), skull base, dorsum of the spinal cord
Symptoms: vague nonlocalizing (headaches, seizures, dizziness) or with focal findings referable to compression of adjacent areas of the brain (e.g. frontal - motor and/or speech depends with Brodmann area/s are affected, gaze preference; temporal - deafness or superior quadrantanopsia if Meyer's loop is affected or amnesia & mood disorders if the limbic/parahippocampal lobe is affected, parietal - somatosensory, apraxia, agraphia, acalculia, astereognosis, loss of 2-point discrimination; calcarine/occipital - blindness/visual field defects)
Diagnostics: MRI (densely enhancing extra-axial tumor arising from the dura; dural tail consisting of thickened, enhanced dura extending like a tail from the mass)
Differential diagnosis: dural metastasis

𝐖𝐇𝐎 𝐆𝐫𝐚𝐝𝐢𝐧𝐠:
WHO grade I
- grow as well-defined durabased masses
- may compress the brain but do not typically invade it
- extension into overlying bone may be present
- histologic patterns:
⠀⠀⠀> meningothelial - whorled, tight clusters of cells without visible cell membranes
⠀⠀⠀> fibroblastic - elongated cells and abundant collagen deposition
⠀⠀⠀> transitional - features of meningothelial & fibroblastic types
⠀⠀⠀> psammomatous - numerous psammoma bodies
⠀⠀⠀> secretory - glandlike spaces containing PAS(+) eosinophilic material
WHO grade II
- Atypical meningiomas
- (+) increased mitotic rate, or
⠀⠀⠀prominent nucleoli, increased cellularity, or
⠀⠀⠀patternless growth, high N-C ratio, or necrosis
- more aggressive local growth
- higher rate of recurrence
- may require radiotherapy in addition to surgery
- histologic patterns:
⠀⠀⠀> clear cell and chordoid - more aggressive behavior,
WHO grade III
- Anaplastic (malignant) meningiomas
- highly aggressive
- morphology resembles a high-grade sarcoma or carcinoma
- mitotic rates are much higher than in atypical meningiomas


𝙿𝚎𝚝 𝙸𝚗𝚏𝚘𝚛𝚖𝚊𝚝𝚒𝚘𝚗


♡ gifted by @tryvegan4theanimals ❤️
♡ frozen on August 2023
♡ this creature belongs to 🆃🆆🅸🅽🅺🅻🅴 ⭐