Polymicrogyria of the Unilateral Temporal Lobe in a Transsexual Patient-Case Report – a Review

This is an interesting case study about an abnormality in a trans woman’s brain. The trans woman did not have epilepsy or any other neurological condition.

This brain abnormality may or may not be related to gender dysphoria. We only have one case here.

The authors suggest that future studies of people with gender dysphoria should look for “possible brain abnormalities of any kind [in] MRI scans.”

Details of the study:

The trans woman had a condition called polymicrogyria in her left temporal lobe. Polymicrogyria is exactly what it sounds like – if you speak Latin.

Basically we all have ridges or folds in the cerebral cortex of our brains called gyri (one gyrus, two gyri). In polymicrogyria the brain develops many small folds during the prenatal period.

Polymicrogyria can have small or severe effects, depending on where it is in the brain. It is most typically associated with epilepsy.

Polymicrogyria in a larger area of the brain is associated with severe problems like developmental delays, problems with speech and swallowing, muscle weakness or paralysis, and seizures that are difficult to control.

The cause of polymicrogyria is generally unknown. In some cases it is caused by prenatal infections or other problems and in some cases there is a genetic link.

Mild cases of polymicrogyria may be more widespread than we realize.

In this case, the polymicrogyria were in a limited area of the brain and were not causing any problems. The question is, could they be causing gender dysphoria?

At this point, we don’t know, we just have an interesting result to follow up on.

Where exactly is the polymicrogyria in this case study? The English of the study is fairly awkward, but this is what I think they are saying.

The lateral sulcus on the left side is missing the ascending branch. In addition, the posterior branch ends at the preoccipital notch because it is interrupted by the polymicrogyria.

The polymicrogyria are in the parietotemporal region.

This would, I think, be near the temporoparietal junction  (TPJ).*

File:Brain - Lobes - Temporoparietal junction.png

The TPJ integrates information and has many functions, from theory of mind and moral behavior to paying attention. What makes the TPJ interesting in discussing gender dysphoria is that the TPJ also plays a role in integrating multisensory signals from your body. The TPJ may be part of how we experience a sense of body self-consciousness, i.e. identifying with your body, self-location, and first-person perspective.

Stimulating the TPJ can cause an out-of-body experience (OBE). (Fascinating study here.)

This study concludes:

“These results suggest that the TPJ is a crucial structure for the conscious experience of the normal self, mediating spatial unity of self and body, and also suggest that impaired processing at the TPJ may lead to pathological selves such as OBEs.”

So it might be possible that polymicrogyria in the TPJ would cause someone to experience a disconnect from their body. Could that cause or contribute to gender dysphoria?

Polymicrogyria are created during fetal development and are not influenced by the postnatal environment, so dysphoria about the body could not cause polymicrogyria.

In addition, if polymicrogyria plays a role in gender dysphoria, it is not related to sex hormones or normal differences between males and females. Polymicrogyria are not a normal part of the brain.

There might, however, be multiple factors that contribute to developing gender dysphoria. Damage to the TPJ might be just one factor or it might only be a factor in some cases.

Another possibility would be that something happened to this trans woman prenatally that caused her to develop gender dysphoria and to have polymicrogyria.

Interestingly, an earlier study of gynephilic** trans women’s brains found that the trans women had larger gray matter volumes than cis men or women in the “right temporo-parietal junction (around the angular gyrus and in the posterior portion of the superior temporal gyrus).”*** You can read more here. This is not the same as what the current study found – polymicrogyria on the left side of the brain – but it is interesting that the TPJ seems to be involved in both studies.

Obviously without more data, this is all very hypothetical.

It would be useful to have more studies that look at the TPJ in the brains of trans and cis people. As always, controls should include some gay and lesbian cis people.

Original Study:

Polymicrogyria of the Unilateral Temporal Lobe in a Transsexual Patient—Case Report by Starcevic, Ana; Zigic, Dusica Markovic; Filipovic, Branislav in Neuroscience and Medicine4.4 (Dec 2013): 263-266.

For more information on polymicrogyria:

Genetics Home Reference on Polymicrogyria (a service of the National Institutes of Health).

Polymicrogyria Awareness group.

*Parietotemporal region may be another way to say temporoparietal junction, I’m not sure. The translation of the article has a lot of problems.

**Gynephilic = attracted to women. Some studies of brain sex look only at trans women (born male) attracted to men, some look only at trans women attracted to women. Studies comparing trans women attracted to men to cis men attracted to women can’t be sure if their results are due to sexual orientation or gender. However, studies that look only at trans women attracted to women leave out half of trans women and may miss important aspects of gender dysphoria. We need more studies that include cis gay and lesbian controls.

The trans woman in the current study had a wife and an ex-wife. She had experienced gender dysphoria since age four. She had a degree in electrical sciences and was “working two jobs which are not in [her] field of professional interest.”

*** The original text refers to the superior temporal gurus. A cool idea, but probably a typo.

Thanks to Wikipedia for the image.

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