What Is a Trigeminal Neuroma?

General Surgery, Oncology

Trigeminal neuroma

Trigeminal neuromas account for 0.2% to 1% of intracranial tumors. Nerve membrane cells originated from the trigeminal nerve myelin sheath. They are usually cystic and hemorrhagic and necrotic. They have envelopes and belong to tumors outside the brain. It originates from the semilunar segment of the trigeminal nerve, is located in the epidural of the middle cranial fossa, grows slowly, and can expand to the cavernous sinus and supraorbital fissure. Originating from the trigeminal nerve root, it is located in the dura of the posterior cranial fossa and can invade the peripheral brain nerves. About 25% of trigeminal neuromas can be located at the tip of the temporal bone rock and span the inner and outer dura of the cranial fossa and posterior cranial fossa.

Trigeminal neuroma disease classification

General Surgery, Oncology

Trigeminal neuroma symptoms and signs

Numbness or pain on one side, loss of masticatory muscles, diplopia, loss of facial sensation and corneal reflexes, atrophy of the temporal and masticatory muscles. Check for eye movements, hearing loss and ataxia.

Clinical manifestations of trigeminal neuroma

The first symptoms are trigeminal nerve stimulation or destruction symptoms, manifested as pain, numbness, etc. in the trigeminal nerve distribution area, of which trigeminal neuralgia is often atypical and lasts a long time. After the tumor enlarges, other cranial nerves or cranial hypertension symptoms appear one after another.

Trigeminal neuroma imaging findings

1.CT performance:

Oval or dumbbell-shaped masses can be seen at the junction of the middle cranial fossa and posterior cranial fossa, showing equal density or low density.

There is generally no cerebral edema around the tumor.

Small tumors may have no placeholder effect. Larger cranial fossa may compress the upper saddle pool; larger cranial fossa may compress the fourth ventricle. Those who ride across the middle cranial fossa and posterior cranial fossa are dumbbell-shaped, characteristic of trigeminal neuroma.

The tumor is strengthened, the smaller solid ones are uniformly strengthened, and the cystic changes are ring-shaped.

The tip of the temporal bone rock was damaged.

2.MR performance:

The mass often spans the middle and posterior cranial fossa, typically with a dumbbell shape.

The middle cranial fossa trigeminal nerve tumor compresses the upper saddle pool and cavernous sinus, and the posterior cranial fossa trigeminal nerve compresses the bridge cerebellar angle and the fourth ventricle.

T1 is weighted as low or equal signal, and T2 is weighted as high or equal signal.

After strengthening, most of them are obviously uniformly strengthened, and a few cystic changes are strengthened in a circle.

There is generally no edema around the lesion.

Etiology and pathology of trigeminal neuroma

Trigeminal neuromas account for 0.2% to 1% of intracranial tumors. Nerve membrane cells originated from the trigeminal nerve myelin sheath. They are usually cystic and hemorrhagic and necrotic. They have envelopes and belong to tumors outside the brain. It originates from the semilunar segment of the trigeminal nerve, is located in the epidural of the middle cranial fossa, grows slowly, and can expand to the cavernous sinus and supraorbital fissure. Originating from the trigeminal nerve root, it is located in the dura of the posterior cranial fossa and can invade the peripheral brain nerves. About 25% of trigeminal neuromas can be located at the tip of the temporal bone rock and span the inner and outer dura of the cranial fossa and posterior cranial fossa.

Trigeminal neuroma diagnostic test

1. Medical history Note whether there is numbness or pain on one side of the face, loss of chewing muscle strength, and double vision.

2. Check the nervous system for facial sensation, corneal reflex, atrophy of the temporal and masticatory muscles. Check eye movements for hearing loss and ataxia.

3. X-ray plain radiographs of the middle cranial fossa of the skull show the bone resorption at the apex of the petrous bone or enlarged with round holes and oval holes. The posterior cranial fossa or dumbbell type showed bone resorption at the tip of the rock bone, but the inner ear hole was not enlarged.

4. CT and MRI scans can clarify tumor size, morphology, and relationship with surrounding tissues, which is of great significance for diagnosis, typing, and choice of surgical approach. CT manifests as the middle or posterior fossa oval or dumbbell-shaped iso-density or low-density shadow, the density of the cystic changes is lower, and the parenchyma is strengthened obviously. MRI showed low signal or equal signal on T1 weighting, high signal on T2 weighting, and showed uniform enhancement after enhancement. No obvious edema around.

Trigeminal neuroma treatment plan

1. The middle cranial fossa type adopts the subtemporal approach, and the lower temporal valve is as close to the base of the cranial fossa as possible to obtain a total resection of the tumor.

2. Posterior cranial fossa type can adopt unilateral suboccipital approach, operation is similar to acoustic neuroma. If the tumor extends in the direction of the rocky slope, a rock-through approach can be used.

3. Dumbbell type can adopt the combined approach of the mastoid rear curtain. The transcranial approach, that is, the anterior sigmoid sinus approach through the cerebellum, can be used to remove tumors in the posterior and middle cranial fossa simultaneously.