Case Study 32 Bilateral ILN LesionA Progressive Walk Through of the Taxonomy of Disorders of Consciousness1

The Parkinson's-Reversing Breakthrough

What is Parkinsons Disease

Get Instant Access

This patient was a male in his middle forties brought to the hospital after he could not be woken up normally in the morning. He was in a low-grade coma, with double incontinence, punctuated by brief periods of restlessness. His clinical and laboratory examinations were generally unremarkable with a blood pressure of 150/90, normal electrocardiogram, and normal metabolic studies. On neurological exam he had narrow pupils nonreactive to light, with the eyes remaining in midposition. Reactions to painful stimuli were predominantly extensor movements and some pained facial expression. Initial structural imaging with contrast enhancing revealed symmetrical bilateral paramedian thalamic lesions (see Fig. 3.2). The lesion was read as extending subthalamically somewhat into the ventral tegmental area. The EEG findings consisted of generalized slowing of background activity, loss of differentiation, and some delta bursting, frontotemporally and centrally. There were repeated bursts of generalized slowing, slow-wave and spike-and-wave discharges, at around 6 per second.

By the third day, there was some restoration of wakefulness and gaze, and the patient gradually transitioned out of the vegetative state. He began to pay more attention to his surroundings in terms of eye tracking but was totally akinetic and mute. One week after admission he remained in this condition. In week 2, he began to show more spontaneous movements, but there was still significant akinesia, with stereotypic movements, such as handling his guitar in a manner suggestive of some efforts to play, but without evidence of much conscious participation, since his movements continued when the guitar was removed. There were other aimless activities such as rubbing his abdomen for long periods of time without any evidence of discomfort. During the third week, the akinetic mute state changed into a more hypokinetic state with

'Case material and graphics from van Domburg, et al. (1996) with permission.

Www Ant Commissure

Figure 3.2. CT Scan of ILN patient and Schematic Graphic of Mesodiencephalic Regions. Key for Mesodiencephalic Graphic: CA = anterior commissure; CP = posterior commissure; ANT = anterior thalamus; IL = intralaminar region; CEM = centromedian ILN; VTA = ventral tegmental area; NRT= reticular thalamus; DL/VL= dorsolateral/ventrolateral thalamus; DM = dorsomedial thalamus; SN = substantia nigra; MT = mamillothalamic tract; EW = Edinger-Westphal nucleus; CS= superior colliculus; CI = inferior colliculus; F= fornix, P = pulvinar; BAS= basilar artery; ACA = anterior communicating artery; ACP = posterior communicating artery. (From van Domburg, P., ten Donkelaar, HJ, Notermans, SH 1996, with permission from Elsevier Science).

Figure 3.2. CT Scan of ILN patient and Schematic Graphic of Mesodiencephalic Regions. Key for Mesodiencephalic Graphic: CA = anterior commissure; CP = posterior commissure; ANT = anterior thalamus; IL = intralaminar region; CEM = centromedian ILN; VTA = ventral tegmental area; NRT= reticular thalamus; DL/VL= dorsolateral/ventrolateral thalamus; DM = dorsomedial thalamus; SN = substantia nigra; MT = mamillothalamic tract; EW = Edinger-Westphal nucleus; CS= superior colliculus; CI = inferior colliculus; F= fornix, P = pulvinar; BAS= basilar artery; ACA = anterior communicating artery; ACP = posterior communicating artery. (From van Domburg, P., ten Donkelaar, HJ, Notermans, SH 1996, with permission from Elsevier Science).

some signs of emotional expression. At the end of week 3, this hypokinesia gave way to excessive unintelligible talking, often slurred, with occasional delusional content, essentially a presentation of a delirium. During this period of confusional state, there was a growing lability (consistent with the resolution of the akinetic affectless state), and much disorganized behavior, including walking away from the ward.

During the fourth week he showed the beginning of the ability to meaningfully engage in neuropsychological assessment but with obvious global cognitive deficits, including a marked constructional apraxia and an obvious amnestic syndrome. Working memory and higher cognitive aspects of executive functions were still quite poor. By the fifth week, he still showed mild language pathology, including frequent semantic paraphasias and obvious dysnomia, along with a continued but improving amnestic syndrome, but improved attentional and executive functions. By this point the confusional state had largely resolved, and he continued to show gradual cognitive improvement over a protracted period of time. At one year out from bilateral paramedian thalamic infarction, a Wechsler Adult Intelligence Scale (WAIS) IQ score was calculated of 118 verbal and 94 performance IQ. By 15 months out, his verbal score had improved to 125 with little change in his performance IQ. There was still a selective downward gaze palsy, with continued incapacity for well-organized independent activity, some loss of initiative, mild forgetfulness, and slightly disturbed balance. Two years after the event there was only selective downward gaze palsy, a slight motivational inertia, and otherwise a virtually complete recovery of overall cognitive function, including short-term memory.

Follow-up EEGs done successively over a period of several weeks to months showed gradual restoration of normal background activity, gradual decline of the frontotemporal dysregulation, and no further signs of epileptiform activity or hypersyn-chronization. One might hypothesize that disruption of ILN participation in the process of ongoing thalamocortical feedback loops generates disinhibition of nRt-related spike wave and slow-wave discharges, as the nRt's inhibitory control over thalamocortical gating is disinhibited by the loss of ILN glutamatergic projections. During the earliest portion of this evolving syndrome, the EEG findings were similar to those found in absence seizures (and this is exactly how patients with PVS present).

Contrary to widespread clinical folklore on this issue, lesions restricted to the ILN virtually never generate a sustained coma. Several of these restricted paramedian tha-lamic vascular insults consistently show the fascinating syndrome of walking through the taxonomy of disorders of consciousness, beginning with the most severe and proceeding to the least severe. The clinical presentation begins with a brief period of initial coma lasting hours to days, followed by a restricted period of persistent vegetative state, oftentimes a more protracted period of akinetic mutism, and then typically a period of confusional lability, finally yielding various degrees of long-term baseline cognitive deficit. In some instances, the cases involve a nearly full recovery with only residual disorders of downward gaze, a finding presumed secondary to the disruption of intralaminar connections between brainstem ocular motor systems and the frontal eye fields. (See later discussion of intralaminar nuclei function for more details.) The initial period of akinetic mutism in this particular case may also have had some contributions from the partial disruption of the ventral tegmental area, as massive lesions of this tend to generate severe and largely unremitting AKM. However, other cases without VTA involvement show this progression, so it is unlikely that the VTA lesion played a major role in determining the clinical presentation.

Was this article helpful?

0 0
Anxiety and Depression 101

Anxiety and Depression 101

Everything you ever wanted to know about. We have been discussing depression and anxiety and how different information that is out on the market only seems to target one particular cure for these two common conditions that seem to walk hand in hand.

Get My Free Ebook


Post a comment