Thread by @MedinaRiojaMD

Midbrain Syndromes: Parinaud, Weber, Benedikt, Claude and Nothnagel.
🧠🥸🤔

#NewYearNewThread

#Neurology #Anatomy #Neurotwitter #History

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Before we describe the main characteristics of these syndromes, it is improtant not to forget the main structures present in this region. ⚠️

Note: this is not a neuroanatomy 🧵

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Structures not to forget at this level:

1️⃣ Corticospinal tract: motor function (contralateral)
2️⃣ Oculomotor nucleus: CN III👀
3️⃣ 🔴 Nucleus: rubrospinal tract 🦾 (arm flexion)
4️⃣ Subst Nigra: basal ganglia relay (more complex than that)
5️⃣ Inf Colliculus

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Oculomotor nucleus ⁉️ CN III
More like oculomotor complex: each subnuclei have especific functions.
🥸
👇

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Do you know how to tell the difference between a nuclear CN III lesion vs an infranuclear CN III lesion? 👀

Answer in the next couple of days.

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Vertical gaze control❓

Three nuclei (more complex than that)

1️⃣ riMLF
2️⃣ Interstitial nucleus of cajal
3️⃣ N of Darkschewitsch

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Structures not to forget at this level:

1️⃣ Corticospinal tract: motor function (contralateral)
2️⃣ CN IV nucleus: oblique superior👀
3️⃣ Inf Colliculus: 👂

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After this "brief" review we can deduce that midbrain lesions will cause:
🤔

1️⃣ Weakness
2️⃣ Oculomotor abnormalities (CN III and IV)
3️⃣ Hyperkinetic movement disorders (involvement of the 🔴 nucleus?)
4️⃣Parkinsonism

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Time to review some syndromes❗🤯

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🥇 Benedikt (1889)

1️⃣ Oculomotor palsy (CN III)
2️⃣ Contralateral hemiparesis
3️⃣Contralateral invountary movements/tremor

Lesion: 🔴 N, corticospinal, CN III N

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🥇 Benedikt (1889)

Tremor seen here, has the same phenomenology as Holmes (Rubral 🤔❓)Tremor. (3–4 Hz flexorextension oscillation, present at rest and exacerbated with posture and additionally intensified with action)

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So, who described this peculiar type of tremor first?
📜🧠

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Answer:

Benedikt (1899), Gordon Holmes published his description in 1904.
🤔

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🥇 Benedikt (1889)

Rubral❓
Is it always due to a 🔴 N lesion?

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Answer:

In a case-series published in 2016 in #Neurology, the most Fx lesion localizations that caused "Holmes" tremor were:

1️⃣Midbrain
2️⃣Thalamus
3️⃣ Other (including cortical localizations)

🔴 N lesions may not cause "rubral tremor" 🤯

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🥈 Claude (1912)

1️⃣ Oculomotor palsy (CN III)
2️⃣ Contralateral cerebellar abnormalities (ataxia, asynergia, etc)

Lesion: Superior Cerebellar Peduncle, CN III,IV N

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🥉 Nothnagel (1879)

1️⃣ Oculomotor palsy BILATERAL (CN III)
2️⃣ Gait ataxia

Lesion: Both: superior Cerebellar Peduncle, sup and inf Colliculi

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🍀 Parinaud: Nothnagel like

1️⃣ Vertical gaze paresis
2️⃣ Convergence retraction nystagmus
3️⃣ Bilateral upper eyelid retraction
4️⃣ Light/near dissociation of the pupils

Lesion: dorsal midbrain

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🍀 Parinaud

Were all the previous elements present in Parinaud's original description?🤔🧠

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🍀 Parinaud
No, actually:

He emphasized the association between vertical gaze paralysis accompanied the convergence paralysis.

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🕔 Weber syndrome (1863)

1️⃣ Oculomotor palsy (CN III)👀
2️⃣ Contralateral hemiparesis

Lesion: CN III N, Corticospinal tract

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Did you like the 🧵?

Never forget that brainstem anatomy is complex, simplification is a 🔑 asset for the clinician🥼, oversimplification may not be useful. I hope I have achieved the first one ⚖️

Happy New Year!

Sources:
1.- Board Review Series. Neuroanatomy. Fifth Ed. 2014
2.- Blumenfeld H. Neuroanatomy Through Clinical Cases, 2010
3.- Neuroanatomy, Interstitial Nucleus of Cajal. From: pubmed.ncbi.nlm.nih.gov/31613454/
4.- Neurology. 1992 Sep;42(9):1820-2. doi: 10.1212/wnl.42.9.1820

Sources:
5.- Neurology. 2016 Mar 8;86(10):931-8. doi: 10.1212/WNL.0000000000002440
6.- Radiographics. 2019 Jul-Aug;39(4):1110-1125. doi: 10.1148/rg.2019180126
7.- Am Orthopt J. 2014;64:126-33. doi: 10.3368/aoj.64.1.12