Neurology -- Correspondence for Di et al., 68 (12) 895-899

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Correspondence published:

Reply from the Authors: Hai-bo Di, Xuchu Weng, Steven Laureys, Yizhang Chen (8 May 2007)

Cerebral response to patient’s own name in PVS and MCS cases: Calixto Machado (8 May 2007)

Reply from the Authors 8 May 2007

Hai-bo Di,
Zhejiang University School of Medicine,
Hangzhou 310006, China,
Xuchu Weng, Steven Laureys, Yizhang Chen
Send Correspondence to journal:
Re: Reply from the Authors

dihaibo1{at}yahoo.com.cn Hai-bo Di, et al.

We appreciate Dr. Machado's comments and agree that the use of different modalities of neuroimaging techniques might provide further possibilities for diagnosing and providing outcome in vegetative and minimally conscious states.
As Dr. Machado correctly pointed out, fMRI and other imaging techniques that measure hemodynamic responses, while retaining many advantages, have relatively poor temporal resolution. [7] EEG, event related potentials and other neurophysiological techniques can directly monitor neuronal activities in millisecond scale and can be used on bedside. There, it is reasonable to expect that the combination of these two complementary imaging modalities would surely provide a better choice for detecting the residual cortical functions in the patients with vegetative and minimally conscious states. [5, 7, 8]
For this very reason, we are currently conducting an ERP study with the stimuli similarly discussed in this paper. [1] We look forward to learning more about Dr. Machado's interesting work.
References
5. Kotchoubey B, Jetter U, Lang S, et al. Evidence of cortical learning in vegetative state. J Neurol 2006;253:1374-1376.
6. Owen AM, Coleman MR, Boly M, et al. Detecting awareness in the vegetative state. Science 2006;313:1402.
7. Coleman MR, Menon DK, Fryer TD, et al. Neurometabolic coupling in the vegetative and minimally conscious states: preliminary findings. J Neurol Neurosurg Psychiatry 2005;76:432-434.
8. Perrin F, Schnakers C. Brain response to one's own name in vegetative state, minimally conscious State, and Locked-in syndrome. Arch Neurol 2006;63:562-569. Disclosure: The authors report no conflicts of interest.

Cerebral response to patient’s own name in PVS and MCS cases 8 May 2007

Calixto Machado,
Institute of Neurology and Neurosurgery
Institute of Neurology and Neurosurgery Apartado Postal 4268, Cuba
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Re: Cerebral response to patient’s own name in PVS and MCS cases

braind{at}infomed.sld.cu Calixto Machado

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Di et al evaluated vegetative and minimally conscious states cases and the differences in brain activation in response to presentation of the patient’s own name spoken by a familiar voice. They concluded that the cerebral responses assessed by fMRI might be a useful test for distinguishing “minimally conscious state–like cognitive processing” in some cases, clinically diagnosed as vegetative state. [1]
Staffen et al have also examined fMRI brain response in a PVS patient while hearing his own first name and another name, concluding that the patient showed differential cortical processing in the medial prefrontal cortex, when both auditory stimuli were compared. [2]
We recently studied a patient fulfilling PVS clinical criteria with quantitative electric tomography (QEEGt), a technique that combines anatomical information of the brain by MRI with EEG patterns, to estimate the sources of the EEG within the brain. [3, 4] In our patient, we found EEG activation in the gamma band when he listened to his mother’s voice, localized in the lateral and posterior regions of the left hemisphere. Considerating previous studies of gamma coherence and consciousness generation, this finding might suggest recognition of the mother’s voice and high-level residual linguistic processing. [4]
Other authors have also reported that some PVS case showed a high-level cortical processing, using event related potentials. [5] It is also important to consider the time and space resolutions in assessing brain function comparing neurophysiologic with other neuroimaging methods. It is well known that EEG, event related potentials, and other neurophysiologic techniques have a high time resolution which allows assessing early brain functional changes in milliseconds. Cerebral blodd flow measurements achieved by fMRI, PET and SPECT were expressed in the brain within seconds and minutes. Moreover, QEEGt solves the low spatial resolution of EEG estimating the sources of bioelectric generators inside the anatomical voxels of the patient’s MRI. [3, 4]
Although vegetative and minimally conscious states are classified as dissimilar clinical entities, boundaries between different disorders of consciousness must be further outlined. The use of different modalities of neuroimaging techniques might provide further possibilities for diagnosing and providing outcome in these states.
References
1. Di HB, Yu SM, Weng XC et al. Cerebral response to patient's own name in the vegetative and minimally conscious states. Neurology 2007;68:895-899.
2. Staffen W, Kronbichler M, Aichhorn M, Mair A, Ladurner G. Selective brain activity in response to one's own name in the persistent vegetative state. J Neurol Neurosurg Psychiatry 2006;77:1383-1384.
3. Bosch-Bayard J, Valdes-Sosa P, Virues-Alba T et al. 3D statistical parametric mapping of EEG source spectra by means of variable resolution electromagnetic tomography (VARETA). Clin Electroencephalogy 2001;32:47-61.
4. Machado C, Cuspineda E, Valdes P et al. Assessing acute middle cerebral artery ischemic stroke by quantitative electric tomography. Clin EEG Neurosci 2004;35:116-124.
5. Kotchoubey B, Jetter U, Lang S et al. Evidence of cortical learning in vegetative state. J Neurol 2006;253:1374-1376. The author has nothing to disclose.