Wednesday, 22 September 2010

Sociopathic Dementia

Frontotemporal dementia (FTD) is a tragic, but scientifically fascinating, disease.


FTD only accounts for a small fraction of dementias in total (estimates range from 2% to 10%), but it typically strikes people aged in their 50s or 60s, i.e. much earlier than the average for Alzheimer's disease, the most common cause of dementia. As a result, FTD accounts for a large proportion of early-onset cases.

The symptoms are different to those of Alzheimer's, at least in the early stages. Memory problems and confusion are not prominent. Nor are hallucinations and delusions, which are seen in 20% of Alzheimer's, but only 2% of FTD.

Instead, patients often present with language problems - either forgetting what words mean, starting with uncommon words and progressing to easy ones ("semantic dementia"), or losing the ability to articulate speech ("nonfluent aphasia").

But the most disturbing effects are behavioural and personality changes. These are not seen in all cases, but in some people (the "behavioural variant"), they are the main symptom. Patients may begin to act entirely out of character, including criminal acts.

Aggressive behaviour is also sometimes seen in Alzheimer's, but it's usually associated with confusion or hallucinations: people "don't know what they're doing". In FTD, patients can commit serious crimes even though their cognitive function is pretty much intact: they do know what they're doing.

Mario F. Mendez discusses this in a new paper, The Unique Predisposition to Criminal Violations in Frontotemporal Dementia, and asks whether people who commit crimes while suffering from FTD should be considered legally responsible for their apparantly "sociopathic" actions. He presents 4 case histories.
Patient 1: A left-handed male in his sixties began stalking and attempting to molest children for the first time in his life. He followed children home from school and tried to touch them... On another occasion, he stood at the foot of a pool and stared at the children for a prolonged time.

When he exposed himself to his neighbor’s children, he was arrested. The patient did not deny his actions, could describe them in detail, and endorsed them as wrong and harmful. Despite this, he stated that he did not feel that he was causing harm at the time of his acts.


The patient’s personality had deteriorated over the prior four years, with decreased concern for others, disinhibition, and compulsive hoarding. He had caused disturbances at work, such as intruding into others’ conversations and walking into others’ offices... constantly pilfering... hiding money.... In addition, he ate indiscriminately, even going through waste containers and eating garbage. He stopped showering and wore the same clothes every day.
Neuropsychological testing and brain scans suggested early FTD, and his mother had reportedly suffered unspecified dementia; FTD is often genetic. He was not prosecuted. This case has a lot in common with the man who became a pedophile after surgery for a brain tumour: not just the pedophilia, but other symptoms like compulsive hoarding, over-eating, etc.
Patient 4: A right-handed man in his early fifties had a hit-and-run accident and left the scene without concern. He had struck a van with passengers but kept driving. The police stopped him a short distance away from the scene, and he did not deny his action.

Leaving the scene of an accident was not characteristic of his premorbid personality, yet he had had several recent traffic violations... He could recall and describe the accident, knew that it was wrong to leave the scene, but did not feel the need to stop at the time.


Over the prior two years, the patient’s pervasive behavior had significantly changed. He had become disengaged and emotionally detached; for example, he did not react to the death of his mother...

He was no longer embarrassed over passing gas or belching in public or
appearing partially clothed in front of others. The patient had a tendency toward hyperorality, especially for peanuts, and had a decline in personal hygiene. Other aspects of the history included dysarthria and a recent tendency to choke on liquids.
This patient showed clear signs of motor neuron disease, which occurs in up to 15% of FTD cases. He died, as a result of the progression of the motor neuron disease, one year later, after developing other symptoms of FTD. His death meant he could not be tried for the hit-and-run.

Mendez notes that legally, these patients would probably not qualify for the "insanity defence". Under the British M'Naghten Rules, also adopted by the USA, the defendant is only eligible if they were
labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong.
These patients do not fit that bill.

Finally, why does FTD cause sociopathic behaviour? Mendez says that it is because it involves degeneration of the vmPFC, linking FTD patients to the classic case of Phineas Gage whose vmPFC was destroyed by a flying iron rod. But Gage, while he did show personality changes, actually managed to function fairly well in society.

So temporal lobe degeneration probably also contributes to the FTD behavioural syndrome, especially since many of the symptoms (like compulsive eating) are seen in monkeys with temporal lobe lesions.

ResearchBlogging.orgMendez MF (2010). The unique predisposition to criminal violations in frontotemporal dementia. The journal of the American Academy of Psychiatry and the Law, 38 (3), 318-23 PMID: 20852216

14 comments:

Anonymous said...

Although it is certainly true that FTD would be a necessary "cause" to explain the types of disinhibition behavior you describe, I doubt it would be a sufficient cause. In other words, premorbid personality would likely help shape or explain the particular form or expression of disinhibition (e.g. molestation, eating, etc.) For example, in the child molestation case you discuss, it is probable that this unfortunate man had long suppressed or, yes, even repressed, such urges and had the cortical integrity to withstand such impulses. But when his cranium began to atrophy, the neuroanatomical substrate of the "ego" was destroyed, leaving him prey to his id.

ex-hedgehog freak said...

Interesting. Do the cholinesterase inhibitors have any effects in this type of dementia? Or is the underlying pathology that different?

veri said...

So people may be vulnerable to demonic beh. when their G-d module is tampered with. My guess is both described were not religious so indeed they relied on a brain region to define their values. Very interesting. Thanks Neo :)

Anonymous said...

Since alzheimer's can only be definitely diagnosed at autopsy, how reliable are the scans in this condition?

Neuroskeptic said...

ex-hedgehog freak: I don't know anything about treatment of FTD but I don't think so. Cholinesterase inhibitors are used to improve memory and attention, but these are not the main problem in FTD.

Anonymous said...

veri if you don't take the meds we gave you on your parole discharge it will be revoked!

veri said...

Go ahead, cuff me.

Anonymous said...

veri you have 3 options:

- take your meds
- get back to the psychiatric ward on our own
- let the devil take care of you...

veri said...

I don't appreciate the bullying. Just, leave me alone.

Anonymous said...

Why do the case histories mention their handedness? What differences does it make?

veri said...

Historically they used to kill people for being left-handed. I'm sure the discernment here isn't to do with that but the distinction may've evolved from that mentality. Lefties were considered evil. It was one of justifications for the Holocaust, most Jews are left-handed? ..maybe because they write from right to left?

Anonymous said...

@veri
Well, yeah, I know about those historical prejudices. But I doubt that's the reason the handedness of the patient would be included in a modern case history.

I have heard that left-handedness can result from brain damage early in life, and I was thinking it might have something to do with that.

Neuroskeptic said...

I don't think that handedness is especially relevant to FTD, but it's common to give handedness in neurological studies because with some things, it does matter. And FTD often affects one side of the brain more than the other.

Anonymous said...

veri:
Are you left-handed or right- handed?