Where Gliomas Start — And Why Location Should Shape Surgery

Frontal Lobe Gliomas - Networks that Matter

Post 1: Frontal Lobe

About this series. Over the next few posts, we’ll look at where adult gliomas most often begin and which brain networks are at risk. The goal is plain-English guidance on how location shapes planning, mapping, and recovery—what patients and families actually feel, and how teams try to protect those functions.

Why start with the frontal lobe?

Because it’s the most common site for adult gliomas. In high-grade glioma, the amount of tumor removed correlates with survival. The art is doing more safely—and “safe” depends on circuits as much as it does on anatomy.

Takeaway: The best operations remove as much tumor as possible while preserving the networks that support speech, initiation, planning, and motivation.

The frontal highways: a map you can picture

Think of the brain as a city with long “avenues” (white-matter tracts) connecting neighborhoods (cortical regions):

• Front ↔ Back (anterior ↔ posterior): Many language and control pathways run from the front of the brain (frontal lobe) to the sides/back (temporal/parietal lobes).

• Top ↔ Bottom (dorsal ↔ ventral): Language uses two main routes—a top (“dorsal”) route for sound-to-speech-motor control and a bottom (“ventral”) route for meaning.

• Midline arc: A curved “service road” (the cingulum) runs under the midline, linking motivation and attention systems.

Below are the major tracts you’ll hear about, in simple terms.

The main tracts—what they connect, what they do, what can go wrong

1) Arcuate fasciculus / Superior Longitudinal Fasciculus (AF/SLF) — the dorsal language route

• From → To (direction): Back/side of the brain (posterior temporal & parietal) ↔ inferior frontal (Broca area). Arches around the side of the brain—front to back along the top route.

• Job (big picture): Turns sounds into accurate, well-timed speech; supports word repetition and phonology (the sound-structure of words).

• If affected (examples): “I know the word, but it comes out scrambled,” trouble repeating phrases, mixing up sounds in a word (“papple” for “apple”), needing more time to get words out.

2) Extreme Capsule / Uncinate fasciculus (EC/UF) — the ventral language route

• From → To: Inferior frontal ↔ anterior & middle temporal (semantic hubs). Runs front to back along the bottom route, close to the base of the brain.

• Job: Helps words carry meaning and nuance; links language to memory and emotion.

• If affected: Fluent but “empty” speech, using nonspecific words (“that thing”), trouble understanding less common words, losing shades of meaning, or mixing closely related words (coffee/tea).

3) Frontal Aslant Tract (FAT) — the starter cable for speech and action

• From → To: Pre-SMA/SMA (medial frontal “starter” zones) ↔ inferior frontal gyrus (speech planning). Short front-to-front connector.

• Job: Initiation—kicking off speech and goal-directed actions.

• If affected: “The words are in my head but won’t start,” long pauses before speaking, effortful initiation, sometimes stuttering-like stops/starts.

4) Cingulum bundle — the midline motivation/attention arc

• From → To: Curves under the cingulate from frontal toward parietal/temporal inner surfaces—front to back along the midline.

• Job: Keeps motivation, attention, and “drive” online; part of the Default Mode Network (DMN).

• If affected: Abulia (reduced drive), slower mental “get-up-and-go,” trouble starting tasks without prompts; family may describe the person as “present but not initiating.”

5) Frontoparietal Control Network (via SLF II/III and related fibers) — the project-management system

• From → To: Dorsolateral prefrontal cortex (DLPFC) ↔ posterior parietal—front to back along the top/side.

• Job: Working memory, set-shifting, planning—keeping goals in mind while you act.

• If affected: Difficulty juggling steps (e.g., cooking a multi-step meal, paying bills), mental fatigue with complex tasks, “I can do each step, but I lose the thread.”

Note on dominance: For most right-handers, language is left-lateralized, but not always. Tumors can also “rewire” function. That’s why teams check dominance before deciding whether to do awake mapping.

A special frontal syndrome to know: SMA syndrome

• Where: Supplementary motor area (SMA) on the inner surface of the frontal lobe (near the top/middle).

• What it looks like: Temporary reduction in initiation—hesitant speech, slowed movements, less spontaneous action.

• Course: Common after medial frontal surgery and usually improves over weeks to a few months. Early explanation and therapy help families understand that it’s expected—and usually transient.

What patients and families might notice (real-world examples)

• Language—dorsal route issues (AF/SLF): Struggling to repeat a sentence exactly; words come out with swapped sounds; phone calls feel harder than face-to-face conversation.

• Language—ventral route issues (EC/UF): Conversations sound fluent but light on specifics; using placeholders (“this,” “that”); trouble finding low-frequency words; misunderstandings with similar concepts.

• Initiation—FAT/SMA: Long pauses before speaking or moving; “he’s quieter, not because he doesn’t know—he can’t get started.”

• Executive control—FPN: Bills unpaid not from neglect, but because multi-step tasks stall; starting dinner is fine, coordinating side dishes crashes the system; difficulty switching from one plan to another.

• Motivation/DMN—cingulum: Less spontaneous activity, needs prompting to begin tasks; family describes a “personality flattening” without sadness—more apathy than depression.

How care teams account for this

• Before surgery: Individualized maps (tractography of FAT, AF/SLF, EC/UF, cingulum) and functional lateralization (fMRI or nTMS) help decide awake vs. asleep and shape the task list if mapping is planned.

• During surgery: Direct cortical and subcortical stimulation can test speech initiation, semantics, repetition, and executive control in real time. This often allows a wider but safer resection near eloquent tracts.

• After surgery: Early, targeted rehab—speech-language therapy tuned to the affected stream, initiation strategies for SMA-pattern deficits, and practical executive-function tools (checklists, chunking, timers).

Bottom line: In the frontal lobe, understanding where the tracts run—and what they do—lets teams remove more tumor while protecting the functions people notice most in everyday life.

Fast FAQ

Is awake surgery always needed in the frontal lobe?
No. It’s used when real-time testing is likely to change decisions near eloquent tracts. Otherwise, surgery proceeds asleep, guided by preoperative mapping.

If SMA symptoms happen, how long do they last?
They typically improve over weeks to a few months. Planning for this and starting therapy early make a difference.

Why not stop early to avoid any risk?
Because in high-grade glioma, more complete removal is associated with better survival. The goal is to remove more and protect the right connections.

Next in the series

Temporal lobe gliomas: seizures, memory circuits, and how the dorsal vs. ventral language streams change the operative plan.