Explaining the Brain: Cerebrum & Cerebellum

The CEO and the Project Manager: Understanding Cerebrum and Cerebellar Injuries

Meet Randal

Randal came home from ten years of serving in the army. As a veteran, he was walking and talking fine per his doctor's reports, but his wife, Carmen, noticed his usual mojo was off. "He used to plan everything," she said. "Now, he can’t even finish writing a grocery list, never mind the actual shopping. He gets frustrated, his temper flares, and he seems... just different."

The Pathology: The Jello "Slosh" and the Damaged "Spiderweb"

Randal spent a lot of his time in the army near explosive devices. As a young man he refused to wear hearing protection, like a lot of his fellow soldiers. He didn’t know that this choice was not just damaging to his hearing, it also likely caused repeated blast damage to his brain. 

When Randal was near an explosion, his brain experienced a violent "slosh." Because the brain is the consistency of jello, each pressure wave moved through his skull which caused the brain to deform and ripple.

As the brain sloshes, the Cerebrum (the large, upper part of the brain) scraped against the sharp, bony interior of the frontal skull. This disrupts the areas responsible for personality and decision-making.

As we learned in Lesson 1, the brain relies on White Matter, the insulated "wires" or axons to communicate across areas of the brain.

A blast causes Micro-cavitation: Tiny bubbles form and collapse in the brain fluid, creating a "shearing" force.

Focal Injuries are like a bruise on an apple (one specific spot of damage).

Diffuse Injuries are more like a spiderweb that has been shaken by a ferocious wind storm. The web looks intact, but the individual silk strands are stretched or snapped throughout. This is why Randal’s MRI looks normal, but his brain’s "connectivity" is on the fritz.

The CEO (Cerebrum) vs. The Project Manager (Cerebellum)

To help Carmen understand Randal's "clunky" behavior, we look at Functional Connectivity: How the CEO and Project Manager talk to each other.

• The Cerebrum (The CEO): This is the large "Front Office." It handles the high-level vision: "I need to pay the bills" or "I want to tell a joke."

• The Cerebellum (The Project Manager): Tucked under the back of the cerebrum, the Project Manager doesn't come up with the ideas, but it handles the timing, rhythm, and force.

When the Project Manager is glitching, it's because the "wires" between the CEO and the Project Manager are stretched (Diffuse Axonal Injury). We call the resulting effect: Cerebellar Cognitive Affective Syndrome (CCAS).

Randal's thoughts aren't just "lost,” they are mistimed. He’s not "just an angry person now"; his emotions are unregulated. It’s like a Project Manager who forgot to check the volume on a speaker before the CEO shouts: “Is this thing on?!” into the microphone. Randal is just as surprised and frustrated by moments of impulsive anger, laughing, or crying as his wife is. 

Clinical Implications for Rehab

Because Randal’s injury is like a wind-torn spiderweb affecting the connectivity across major areas of his brain, we should look at two key rehabilitation strategies across all care teams. 

1. Repairing Communication Between the CEO and Program Manager:

    Since the "wires" (White Matter) of the Cerebrum are damaged in blast injuries, we suggest using Rhythmic Entrainment to help. Using a metronome or music with predictable tempos can help the Cerebellum "re-time" the Cerebrum’s messages. Link music or metronome timing to simple tasks, and increase the difficulty of the task or increase the pacing of beats to increase functional connectivity. 

   
   

2. Reducing CEO Fatigue in Rehabilitation Sessions: 

   Because Randal's Cerebrum is working twice as hard to send signals over broken wires, Randal will have a lot of cognitive fatigue. Rehab-focused sessions must include frequent brain breaks to prevent the CEO from crashing. Plan in 60 seconds of silence with eyes closed, and water breaks several times throughout sessions. Check in with your client before they drive home and allow them to rest their brain for 10-15 minutes in the lobby or in their car before they attempt to drive. If they appear too fatigued (as evidenced by significant affect changes, confusion, nodding off, and cognitive status changes) call for a Med Ride service or contact their emergency contact to pick them up. 

What to Look For:

Feature	Cerebrum-Heavy (CEO)	Cerebellum-Heavy (Project Manager)
Primary Issue	Cognition: Logic, memory, and "What" to do.	Regulation: Timing, rhythm, and "How" to do it.
Physical Sign	Contralateral weakness (opposite side of injury).	Ataxia: Clumsy, uncoordinated movement on the same side.
Speech	Aphasia: Struggling to find the right word.	Dysarthria: Slurred or "scanning" speech (rhythm is broken).
Emotional State	Disinhibition (the "filter" is gone).	CCAS: Emotional "dysmetria" (overshooting or undershooting a reaction).

Download this free clinical tool, ideal for care providers working with survivors and their care partners to conduct a general, quick assessment that allows for improved clinical communication with the survivor, improved care planning, and an introduction to the ways in which the survivor's brain is injured and healing.

CLINICAL TOOL Cerebrum vs. Cerebellum Assessment.pdf

Download PDF • 117KB

Pair it with this free self-report check-in handout for survivors. Ideal for survivors who can read, write, or have a care partner who can help them complete the handout three times before they see you next for evaluating functional connectivity changes or plateau.

Survivor Handout Self Report Tool Cerebrum vs Cerebellum.pdf

Download PDF • 62KB

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