We appreciate the interest of Altschuler et al in our recent article. It is interesting to see that in hemihydranencephaly there seems to be a proclivity for absence of the left hemisphere as pointed out by Altschuler et al. Reviewing the other published cases,16 only 1 patient suffered from a lesion of the right hemisphere,1 which raises the question of hemispheric dominance and whether right-hemispheric hemihydranencephaly is less favorable in the clinical outcome. However, the reported patient who suffered from an absent right hemisphere1 only demonstrated mild mental retardation and contralateral hemiparesis and therefore presents a favorable outcome compared with the others. Which hemisphere is affected seems to be irrelevant to long-term outcome and survival, because reasonable outcome was also reported in the patient with the absent right hemisphere1 and demonstrated in our case7; however, 3 of the patients suffering from left-hemispheric hemihydranencephaly died in the follow-up period (personal communications with the author groups listed in refs 16, 2005) as a result of bronchopneumonia or related pulmonary problems. It cannot be answered, however, if right-hemispheric hemihydranencephaly is more reasonably unlivable.
The remarkable findings in our 36-year-old patient are his motor skills, which enable normal independent living. Impairment is the result of deficits in fine motor control as demonstrated in the Wolf Motor Function Test and the inability to perform the Perdue Pegboard. No aphasia could be found, and intellectual capacities, although not specifically tested, enabled the patient to complete school and vocational training.
As demonstrated in our case, the human immature brain is able to compensate for brain damage, if it occurs in very early childhood, to a remarkable outcome. All the reported patients demonstrated contralateral hemiparesis of various degrees. Our patient presented with strong mirror movements that also seem to become apparent in the Altschuler et al case as well. Mirror movements have been found in congenital hemiparetic patients with projections innervating both-sided motoneuron pools simultaneously by using transcranial magnetic stimulation8; however, mirror movements are physiologic until the age of 10 years and decrease with age9 but have been found in healthy adults during forceful complex movements10 demonstrating ipsilateral projections. As demonstrated by our patient with hemihydranencephaly,7 predefined motor areas such as the precentral gyrus seem to have the capacity to adopt similar or contralateral functions, which are executed by ipsilateral pathways; however, quality of motion and precision differs.
We strongly encourage Altschuler et al and other groups who are managing patients with hemihydranencephaly to join an international work group that we started when reviewing the literature. Because of the rare occurrence of this disorder, studies should be coordinated to answer questions of human brain development in a standardized manner, especially in these patients, giving the opportunity to examine the meaning of hemispheric dominance.
REFERENCES
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