Neurology -- Correspondence for Gaillard et al., 69 (18) 1761-1771

Correspondence published:

Atypical language in lesional and nonlesional complex partial epilepsy: Iraj Derakhshan, Charleston, WV 25301 (15 January 2008)

Reply from the authors: William Davis Gaillard, William H Theodore, Bethesda MD (15 January 2008)

Atypical language in lesional and nonlesional complex partial epilepsy 15 January 2008

Iraj Derakhshan,
Private Practice
415 Morris St, Suite 401,
Charleston, WV 25301
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Re: Atypical language in lesional and nonlesional complex partial epilepsy

idneuro{at}hotmail.com Iraj Derakhshan, et al.

I read Gaillard et al.’s paper on the incidence of atypical handedness and language laterality in a cohort of 102 patients with epilepsy. I would like to make the following comments pertaining to their findings in Table 1 and Figure 1. [1]
The authors found an incidence of 22% for right hemisphere language laterality among their right-handed participants, calling it high and indicative of transfer of language capability from one hemisphere to the other (plasticity). However, data have indicated the presence of the same ratio of "atypical" laterality of speech in normal right-handed participants manifested in occurrences of crossed aphasia in right and left handedness. [2]
The logical conclusion to be drawn from this discrepancy relates to the arbitrary nature of inventory driven laterality determinations and of “thresholding” in fMRI data collection used by the authors in their study. I have also reviewed this. [3, 4] There is a choice in deciding on the laterality of a favorite hand in early childhood (an event long forgotten), but there is no choice as to the laterality of major hemisphere (i.e. hemisphere of action, including that of speech).
Thus, since all actions start from the major hemisphere, the nondominant side lags behind the dominant by an interval equal to the interhemispheric transfer time (IHTT). [3,4] Accordingly, the best non-invasive and inexpensive test for such determinations is bimanual simultaneous drawing of a line or square with the eyes closed. The side with the longer line or larger square is contralateral to the major hemisphere. This method, first described in 1884 by Hall and Hartwell [5], is the functional equivalent of the previously described use of simple reaction time for determination of the laterality of motor control. [3, 4]
Readers may do the same test by moving their outstretched arms to the extremes of right and left and witnessing the distance between the two index fingers; being larger on one side than the other. The side with larger distance between the two index fingers is contralateral to their major hemisphere. [3-5] This corresponds to their behavioral handedness in ~ 80 percent of cases. The remainder are those whose neural (hemispheric) and behavioral (avowed) handedness did not match. [3, 4]
References
1. Gaillard WD, Berl MM, Moore EN, et al. Atypical language in lesional and nonlesional complex partial epilepsy. Neurology 2007;69:1761-1771.
2. Goodglass H, Quadfasel FA. Language laterality in left-handed aphasics. Brain 1954;77:521-548.
3. Derakhshan I. Nonconvulsive status epilepticus with an unusual EEG: a fresh look at lateralities of motor control and awareness. Epilepsy Behav 2006;9:204-210.
4. Derakhshan I. Laterality of motor control revisited: directionality of callosal traffic and its rehabilitative implications. Top Stroke Rehabil 2005; 12:76-82.
5. Hall GS, Hartwell EM. Bilateral asymmetry of function. Mind 1884;9:93-109.
Disclosure: The author reports no conflicts of interest.

Reply from the authors 15 January 2008

William Davis Gaillard,
Children's National Medical Center
111 Michigan Ave NW. Washington DC 20010,
William H Theodore, Bethesda MD
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Re: Reply from the authors

wgaillar{at}cnmc.org William Davis Gaillard, et al.

We thank Dr. Derakhshan for his comments and for drawing our attention to several interesting studies. Goodglass et al.'s study was devoted to language laterality in left-handed patients with aphasia due to a variety of causes so it is difficult to make direct comparisons to our study. [2]
All methods for determining language dominance have some arbitrary features. Ours was based on using a laterality index for cerebral activation during a standard series of tasks. Thus, it is appropriate to draw conclusions in patients based on results using the same technique in healthy volunteers. One difficulty with much of the older literature, including the study of Goodglass et al. which included many patients with post-traumatic lesions, is the lack of full assessment of brain injury that may have been more extensive than could be detected by plain skull x-rays or clinical examination.
Since then, there has been substantial literature based on invasive measures that document language dominance. One of the largest, reported by Rasmussen and Milner [6] and reproduced by several other studies using the intracarotid amytal test(IAT), fMRI, and transcranial doppler indicates left language dominance in right-handed patients to be 96%. Large fMRI and transcranial doppler series of semantic fluency and decision, targeted at Broca’s area, demonstrate 94%n left language dominance in normal right handed volunteers (based on Edinburgh handedness inventory). [7-9]
fMRI may yield more bilateral activation patterns than invasive measures and it is unclear whether this is truly bilateral in the absence of invasive tests which disrupt neuronal function. Finally, there may be more bilateral activation in a larger proportion of normal developing young children. [10]
References
6. Rasmussen T, Milner B. The role of early left-brain injury in determining lateralization of cerebral speech functions. Ann N Y Acad Sci 1977;299:355-369.
7. Pujol J, Deus J, Losilla JM, Capdevila A. Cerebral lateralization of language in normal left-handed people studied by functional MRI. Neurology 1999;52:1038-1043.
8. Springer JA, Binder JR, Hammeke TA, et al. Language dominance in neurologically normal and epilepsy subjects: a functional MRI study. Brain 1999;122:2033-2046.
9. Knecht S, Dräger B, Deppe M, et al. Handedness and hemispheric language dominance in healthy humans. Brain 2000;123:2512-2518.
10. Holland SK, Vannest J, Mecoli M, et al. Functional MRI of language lateralization during development in children. Int J Audiol 2007;46:533-551.
Disclosure: The authors report no conflicts of interest.