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Volume 11 No. 07
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Accepted Papers





Case Reports

Dramatic Cataplexy Improvement Following Right Parietal Surgery

David J. Fam, MD1,4; Prathiba Shammi, PhD2,4; Todd G. Mainprize, MD, FRCSC3,4; Brian J. Murray, MD, FRCPC, D,ABSM1,4
1Divison of Neurology, Department of Medicine, University of Toronto, Toronto, Canada; 2Department of Psychology, University of Toronto, Toronto, Canada; 3Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada; 4Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada

ABSTRACT

This is the case of a 34-year-old woman with severe narcolepsy with cataplexy who experienced a dramatic reduction in cataplexy symptoms after resection of a right parietal astrocytoma. The patient underwent detailed neurological exam, neuropsychological testing, polysomnography and multiple sleep latency testing following surgery.

Citation:

Fam DJ, Shammi P, Mainprize TG, Murray BJ. Dramatic cataplexy improvement following right parietal surgery. J Clin Sleep Med 2015;11(7):829–830.


Narcolepsy is a disorder resulting in disrupted transition between sleep states from an orexin/hypocretin signaling impairment. Cataplexy is the emotionally triggered loss of motor tone, which is pathognomonic. Here we describe the first reported case of dramatic improvement in cataplexy symptoms following resection of a right parietal astrocytoma.

REPORT OF CASE

A 34-year-old right-handed woman had 18 years of narcolepsy with cataplexy. Her symptoms began with multiple daily episodes of cataplexy triggered by virtually any emotional stimulus including the thought of humor. She had sleepiness, daily hypnogogic hallucinations, and sleep paralysis on awakening several times weekly.

Investigations included a multiple sleep latency test (MSLT) showing a short sleep latency and multiple sleep onset REM periods (SOREMPS). She was positive for HLA DQB1*0602. She underwent several medication trials at an outside institution including methylphenidate, dextroamphetamine, modafinil, and fluoxetine. The last of these provided modest improvement in cataplexy. She discontinued all narcolepsy treatment in 2005. She found her symptoms greatly impaired social interactions.

In July 2013, she had worsening occipital headaches. MRI brain showed a right parietal neoplasm. Surgical resection was performed in January 2014 and histology suggested a low-grade astrocytoma (Figure 1).

Preoperative (A) and postoperative (B) T2 FLAIR MRI images of the right parietal lesion before and after resection.

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Figure 1

Preoperative (A) and postoperative (B) T2 FLAIR MRI images of the right parietal lesion before and after resection.

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Immediately after surgery, she had a left homonymous inferior quadrantanopia and trouble performing rudimentary calculations. Despite this, the patient spontaneously reported that she was delighted to experience a dramatic reduction in cataplexy symptoms. For the first several weeks there were no cataplexy events. There were no changes in her medications.

Approximately four months after surgery, she described her cataplexy as at least 75% improved in both frequency and severity compared to baseline. She had increasing social interactions and allowed herself to experience emotions she would otherwise have avoided. She reported minimal improvement in her hallucinations, sleep paralysis, and sleepiness.

On initial examination, she remained fully alert. Affective range of expression was normal. There was an element of receptive dysprosody and difficulty judging the emotional content of speech, including sarcasm. Language examination was normal. She had dyscalculia including difficulty with serial 7's. She had some difficulty with right-left discrimination and identifying her own individual fingers. Further testing for neglect, apraxia, graphesthesia, and stereognosis was unrevealing. Besides her visual field deficits, the remainder of her neurologic exam was normal.

Repeat polysomnography and MSLT from August 2014 again showed a short sleep latency (0.9 minutes) with 4 SOREMPs, consistent with narcolepsy. She continued to endorse that her judgment of emotion and humor was markedly altered post-surgery stating that, “I feel like I'm experiencing some emotions in completely new ways.”

DISCUSSION

Hypocretin secreting neurons in the lateral hypothalamus have been shown to stabilize transitions between REM and NREM sleep through connections in the brainstem. Cataplexy represents muscle atonia in wakefulness that is generally only seen during REM sleep.1 In the majority of cases, cataplexy is elicited by positive emotional stimuli, typically laughter or humor.2 Hypocretin neurons are active during the response to emotional stimuli in humans and project to cortical and sub-cortical areas.1

The amygdala is involved in processing of positive emotional stimuli and linked to modulation of REM control. Recordings from narcoleptic dogs demonstrate firing of the amygdala before and during cataplexy.3 Inhibitory connections between the amygdala and “REM-off” area trigger cataplexy in response to positive stimuli in hypocretin knock-out (KO) mice with a decrease following bilateral amygdala lesions.4 Human studies have shown that narcolepsy patients have altered responses to positive emotional stimuli and reward.5,6

These studies suggest the amygdala and hypocretin neurons are active in response to positive emotional states. The loss of orexin neurons in narcolepsy patients produces unbalanced inhibitory input from the amygdala to the REM-off area resulting in cataplexy. The amygdala has widespread reciprocal projections to many cortical areas, allowing for modulation of top-down processing of emotional content. The non-dominant parietal lobe plays a key role in comprehending emotional interactions.7 It is possible that in our patient, altered emotional processing from a lesion to the right parietal lobe may have contributed to reduction in cataplexy from top-down modulation of the amygdala in the context of orexin deficiency.

One of the limitations of this case report is the relatively short follow-up period. It is conceivable that the patient's improvement may abate with ongoing neuroplasticity.

CONCLUSION

To our knowledge, this is the first reported case of a reduction in cataplexy in a patient with narcolepsy following a cortical lesion. A variety of brain networks, including amygdala connections and cortical modulation of these circuits, likely play a role in triggering cataplexy. The patient's satisfaction with her surgical outcome despite visual field impairment and dyscalculia testifies to the impact that cataplexy has on impairing quality of life. Consideration should be given to following a cohort of narcolepsy patients requiring cortical surgery to assess their long term outcomes.

DISCLOSURE STATEMENT

This was not an industry supported study. The authors have indicated no financial conflicts of interest.

REFERENCES

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