Choroid Plexus (USMLE Focus)
Overview
It is a vascular struc found in ventricles of 🧠 that produces most of the CSF. It plays a role in maintaining CNS homeostasis & is derived from neuroectoderm & pia mater.
Located in: Lateral ventricles, 3rd ventricle, 4th ventricle.
Embryology & Histology
- Origin: Neural tube roof plate + invaginated pia mater
- Epithelium: Ciliated cuboidal epithelium w tight junctions (blood-CSF barrier)
- Core: Fenestrated capillaries & conn T
- CSF is formed via: Active secretion (mainly Na transport → H₂O follows osmotically)
Summary(USMLE Format)
| Feature | Key Info |
|---|---|
| Location | Ventricular system: lateral, 3rd & 4th ventricles |
| Func | Produces CSF (~70%), regulates CNS microenvt |
| Histology | Ciliated cuboidal ependymal cells, fenestrated capillaries |
| Barrier | Blood-CSF barrier (tight juncts betn epith cells) |
| Embryology | Neuroectoderm + pia mater (vascular mesenchyme) |
Clinical Correlations
- Hydrocephalus: Excess CSF due to:
- Obstructive (non-communicating): e.g. aqueductal stenosis
- Overproduction: e.g. choroid plexus papilloma
- Choroid plexus papilloma: Benign tumor → CSF overproduction → hydrocephalus
- Choroid plexus carcinoma: Rare malignant tumor in children
- Infecs: CSF is sampled via lumbar puncture to detect meningitis, encephalitis
- Calcification: Normal w aging (esp. lateral ventricle plexus, seen on CT)
Clinical (USMLE-Style)
Q: A child presents w signs of increased intracranial pressure. MRI shows a mass in lateral ventricle & hydrocephalus. What is the most likely diagnosis?
A: Choroid plexus papilloma – CSF overproduction and ventricular obstruction.
Q: On CT scan of an elderly patient, bilateral calcifications are noted near the trigone of lateral ventricles. What is the most likely explanation?
A: Normal physiological calcification of choroid plexus w age.
Imaging & Diagnostics
- CT scan: Shows location of tumors or calcifications
- MRI (T1, T2): Visualizes soft tissue tumors in ventricles
- CSF analysis: Collected via lumbar puncture → tests for infec, inflamm, malignancy
Physiology of CSF
- CSF volume: ~150 mL
- Produc rate: ~500 mL/d
- Absorption: Arachnoid granulations into superior sagittal sinus
- Funcs: Buoyancy, cushioning, waste removal, nutrient support
Rapid Recall Points
- Choroid plexus = "CSF factory" → mainly lateral ventricles
- Histology: cuboidal ependymal cells, fenestrated capillaries
- Path: Papilloma = overproduction, Carcinoma = rare, calcification = benign aging
- Test CSF for infecs via lumbar puncture
- Imaged via CT/MRI; tumors common in kids (papilloma, carcinoma)
Flashcards
Where is the choroid plexus located?
Lateral, 3rd, &l4th ventricles.
What type of epith cells line choroid plexus?
Ciliated cuboidal ependymal cells w tight juncs.
What forms the blood-CSF barrier?
Tight juncs betn epith cells of choroid plexus.
What is its primary func?
To produce CSF.
How much CSF is produced per day?
Approx'ly 500 mL/d.
What tumor causes CSF overproduction?
Choroid plexus papilloma.
What malignant tumor arises from choroid plexus in children?
Choroid plexus carcinoma.
What imaging is best for choroid plexus tumors?
MRI (best soft tissue resolution).
What condition rslts from obstruction of CSF flow?
Non-communicating hydrocephalus.
What normal finding may be seen in elderly 🧠s
?
Choroid plexus calcification.
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