Imaging findings and differential diagnosis of trigeminal neuroma

Trigeminal neuroma accounts for about 0.
2%~0.
45% of intracranial tumors, accounts for 4%~7% of cranial nerve tumors, the incidence is second only to acoustic neuromas, pathologically divided into schwannomas and neurofibromas, which originate from Schwann cells and nerve fibers
of the nerve sheath, respectively.
Tumors mostly occur at the semilunar ganglion of
the trigeminal nerve.

Clinical manifestations are paresthesias in the trigeminal nerve distribution, and sometimes trigeminal neuralgia is present, but less common
.
Other manifestations include chewing weakness, diplopia, corneal reflexia, hearing loss, ataxia, etc.
, and the larger patients have symptoms
of increased intracranial pressure.

Site of onset

The disease originates from the nerve membrane cells of the myelin sheath of the trigeminal nerve, common cystic degeneration and hemorrhagic necrosis, with capsules, which are extracerebral tumors; It is more common in young adults and is divided into the following types according to the tumor site:

1) Riding across the cranial middle and posterior fossa type: dumbbell-shaped, the most common;

2) Postcranial fossa type: located in the angle area of the pontine cerebellum, the tumor originates from the posterior root of the trigeminal nerve;

3) Medium cranial fossa type, located outside the parasellar dural, the tumor originates from the trigeminal ganglion
of the trigeminal nerve lumen (Meckel cavity) at the base of the skull.

Image representation

CT plain scan: at the junction of the middle cranial fossa and the posterior cranial fossa, the solid part of the oval or dumbbell-shaped mass can be seen as equal or slightly lower density, the cystic area is low density, a few can see the high density and fluid-liquid level caused by bleeding, and the cyst is obviously shaped like a cyst
.
The bone window shows petrous apical bone resorption, orbital superior and inferior fissures and enlargement of the round foramen, and bone resorption
.
Enhanced scanning of solid parts of the tumor and the cyst wall were significantly enhanced
.

MR: The solid part is slightly lower T1 and T2/FLAIR high signal, and the cystic component is T1 low signal and T2 high signal and FLAIR low signal
.
DWI shows no solid fraction or mild diffusion restriction
.
The solid part of the enhanced scan is significantly enhanced, and smaller tumors can be evenly strengthened
.

Brief summary:

1.
The tumor is located in the middle fovea, posterior cranial foveal bridge cerebellar angle area or riding across the middle posterior cranial fovea; Lesions are round-like or dumbbell-shaped; The tumor is solid or cystic; There are many complete envelopes, and the realm is clearer; A small number of tumors may have calcification or bleeding
.

2.
The tumor has a mass effect, and there is no edema or mild edema around it; There is often bone resorption and destruction of the base skull bone and
petrous apical bone.

3.
Non-contrast scanning: the solid part of the CT tumor is equal density or slightly dense, and the cystic part is low density; MRT1WI presents a low signal such as uniform or uneven, and T1WI is mostly an uneven high signal
.

4.
Enhancement: the solid part is more obviously strengthened, and the cystic part is not strengthened
.

5.
Differential diagnosis: 1) acoustic neuroma, meningioma, cholesteatoma; 2) cartilage tumors of petrous bone origin; 3) Vascular tumors
.