Have the abilities of John Lorber's patients with limited cortical mass been further evaluated in adulthood? Short of minor lesions or infarcts, most high-functioning adults have an intact cerebral cortex.  Yet, a surprising result published anecdotally in Science in 1980 caused a lot of scientists to take note of Dr. John Lorber's hydrocephalus patients in England.

Most famously, Lorber reported:


  There's a young student at this university...who has an IQ of 126, has gained a first-class honors degree in mathematics, and is socially completely normal.  And yet the boy has virtually no brain...instead of the normal 4.5 centimeter thickness of brain tissue between the ventricles and the cortical surface, there was just a thin layer of mantle measuring a millimeter or so.


Now, arguing that the subject had "virtually no brain" is perhaps a bit of hyperbole, but the fact remains, he had accomplished an academic feat which many "normal" humans have not.  What's even more astonishing about this particular case is that this subject was purportedly not even aware of his condition until the initial brain scans were performed.

Aside from 1-2 other publications in peripheral journals around the same time period, I have never heard anything further about these patients that Dr. Lorber was following.

In the intervening 30+ years, have there been any follow-up scans/studies of these patients particularly those featuring the mathematics scholar mentioned above?

What mechanisms does the cortex use in these unusual circumstances to counter the effects of decreased cortical thickness?  Are the cortical columns shorter, and in what sense does their connectivity compensate for lower neuron counts/lower cell densities?


  Lewin, R. (1980).  Is your brain really necessary?  Science 210(4475):1232-1234.
It's unclear whether follow-up tests were ever performed on Lorber's patients, and in particular the student referenced by Lewin. Patient confidentiality precludes a systematic search of the literature, particularly because the Lewin (1980) article does not provide a pseudonym with which we can use to track the patient (e.g. "HM"). It is possible that this patient has been the subject of other scientific studies, but there does not appear to be any information that would uniquely identify him as the patient referred to in this article. John Lorber has since passed away (1996), making it unlikely that we'll know for sure.

However, the condition itself has not been ignored. Lorber himself has later studies which look at the brains structure of hydrocephalus patients (Jackson &amp; Lorber, 1984). A more recent study by Feuillet et al. (2007) seems to show similar results with regard to brain tissue, but the IQ of Feuillet's patient was measured at 75. He appeared to function normally in society, but his intelligence is regarded as significantly below average. A news article about this study, including CT images, can be found here.

In 2011, a review article by De Oliveira et al. discussed the above two cases and others. However, no mention of a follow-up to Lorber's original patient is discussed. It seems likely that if a follow-up were performed, it would be mentioned in this review.

There does not appear to be a concrete answer with respect to how these patients can function despite a deficit in cortical tissue. However, De Oliveira and colleagues discuss one hypothesis, as quoted below:


  Computational models such as the “small-world” and “scale-free”
  network might explain clinical resilience in various situations
  (Friston and Price, 2003; Noppeney et al., 2004; Achard and Bullmore,
  2007; Van den Heuvel et al., 2008). Small-world networks predicts that
  neuronal cells are engaged in clustered connectivity with fewer
  long-range connections (Friston and Price, 2003; Achard et al., 2006).
  Thus, there would be a shorter path length between any pair of neurons
  or Brain regions, resulting in higher dynamical complexity, lower
  wiring costs, and resilience to tissue insults. A scale-free network
  is characterized by the existence of a small number of nodes having
  more connections than the other nodes. The nodes that have such a high
  connectivity degree are referred to as hub-nodes and are suggested to
  play an important role in the overall network organization (Friston
  and Price, 2003).
  
  Brain resilience may be also the final result of processes such as
  redundancy, degeneracy, and pluripotentiality of neural systems
  (Friston and Price, 2003; Noppeney et al., 2004). Another possible
  mechanism would be the local neurogenesis already reported in
  structures such as the basal ganglia, with preferential distribution
  in sub-regions of the ventral striatum (Stopczynski et al., 2008).


References


  De Oliveira, M. F., Pinto, F. C. G., Nishikuni, K., Botelho, R. V.,
  Lima, A. M., &amp; Rotta, J. M. (2011). Revisiting hydrocephalus as a
  model to study brain resilience. Frontiers in human neuroscience, 5.
  PDF
  
  Feuillet, L., Dufour, H., &amp; Pelletier, J. (2007). Brain of a
  white-collar worker. The Lancet, 370(9583), 262.
  
  Jackson, P. H., &amp; Lorber, J. (1984). Brain and ventricular volume in
  hydrocephalus. Z Kinderchir, 39(Suppl 2), 91-93.